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‐i‐  

FOREWORD TO THE GRI‐24 CONFERENCE  

The Geosynthetic Research Institute (GRI) is the research arm of the Geosynthetic Institute and has organized and hosted annual conferences since 1987. The first conference was one year after the institute’s founding on August 12, 1986. As such, it was meant to highlight research conducted internally as well as that of its members insofar as their own in-house R & D activities. The first thirteen conferences consisted of a single-theme and thereafter became either three or four theme events. This particular conference, however, reverts back to the original model of having a single theme, i.e., that being one based completely on sustainability. In retrospect, this theme should have been capitalized upon many years ago and perhaps at the very beginning. People in geosynthetics have always known or serious suspected that quarrying sand and gravel, traveling long distances for suitable clay soil, etc., is devastating to the environment in comparison to a comparable alternative of using geosynthetic materials; e.g., the use of geonets or geocomposites in place of granular soils, and geomembranes or geosynthetic clay liners in place of clay materials. The comparison graphic on the front of this proceedings clearly illustrates this fact in that one truckload of geosynthetic clay liners (GCL) is equivalent to approximately 150 truckloads of clay with which to make a compacted clay liner (CCL). What has changed in the intervening years since our original conference regarding sustainability is the clear-cut methodology of quantifying the differences insofar as carbon footprint between traditional and geosynthetic alternatives is concerned. Authenticated values of CO2 produced per unit weight of all construction materials are presently available through environmental agencies in both the United States, the United Kingdom and elsewhere. With these values as a benchmark, comparisons can readily be made. For example, traditional retaining walls vs. MSE walls, plastic pipe vs. concrete and metal pipe, green closure of landfills vs. traditional soil-related covers, embankment erosion protection using geosynthetics vs. concrete or rock armoring, and more are all included in these proceedings. The organization of this GRI-24 Conference on “Optimizing Sustainability Using Geosynthetics,” consists of three sessions with applications in infrastructure, drainage, and waste disposal. All twenty papers have sustainability as their focus. We, the conference organizers and proceedings editors, sincerely thank the authors and speakers for their time and effort in this regard.

  

Conference Organizers and Proceedings Editors Geosynthetic Institute 475 Kedron Avenue

Folsom, PA 19033 USA

George R. Koerner Robert M. Koerner Marilyn V. Ashley Y. Grace Hsuan Jamie R. Koerner

‐ii‐  

ACKNOWLEDGMENTS The Geosynthetic Institute (GSI) is an umbrella organization which encompasses all facets of geosynthetic materials. The five sub-institutes focus on research, education, information, accreditation and certification. A conference such as this one contains all of these activities. Clearly, research is being presented. Obviously, the effort is meant to be educational. Additionally, these proceedings form an information outlet which is available to all who are interested. Lastly, the important issues of accreditation and certification influence all of our undertakings. The institute itself is open to all organizations involved or interested in geosynthetics. This includes government (federal, state and local) agencies, facility owners, designers, consultants, testing laboratories, quality assurance organizations, resin and additive suppliers, manufacturers, manufacturer's representatives, contractors, installers, and research institutes. Recent categories of Affiliated Organizations and Associate Members have been added to facilitate international outreach and to include state regulatory agencies, respectively. Information is available on our Home Page at <www.geosynthetic-institute.org> or from the editors of these proceedings. We wish to acknowledge and thank all of the GSI members and associate members for their support of our endeavors. The current organizations (in the order in which they joined the institute) and their representatives are as follows. Current Board of Director members are identified accordingly. Full Members of the Geosynthetic Institute GSE Lining Technology, Inc. - Boyd Ramsey [BoD] AECOM - Kevin McKeon/Ken Bergschultz/John Trast U.S. Environmental Protection Agency - David A. Carson E. I. DuPont de Nemours & Co., Inc. - John L. Guglielmetti/David W. Timmons Federal Highway Administration - Silas Nichols/Daniel Alzamora Golder Associates Inc. - Mark E. Case/Jeffrey B. Fassett/Paul Sgriccia Tensar International Corporation - Joseph Cavanaugh Colbond Geosynthetics - Joseph Luna/Adrian Dobrat Geosyntec Consultants - Steve Poirier Syntec Corp. - Aigen Zhao LyondellBasell Industries - Fabio Ceccarani/Melissa Koryabina TenCate Geosynthetics - John Henderson/Chris Lawson CETCO - James T. Olsta/Tim Rafter Huesker, Inc. - Steven Lothspeich/Dimiter Alexiew NAUE GmbH & Co. KG - Georg Heerten/Kent von Maubeuge [BoD] Propex - Derek Bass/Judith Mulcay Fiberweb, Inc. - Frank Hollowell/William Walmsley/Brian H. Whitaker NTH Consultants, Ltd. - Rick Burns/Robert Sabanas TRI/Environmental Inc. - Sam R. Allen [BoD] U. S. Army Corps of Engineers - David L. Jaros [BoD] Chevron Phillips Co. - Rex L. Bobsein [BoD] URS Corp. - John C. Volk Solmax Géosynthétiques - Robert Denis

‐iii‐  

Envirosource Technologies, Inc. - Douglas E. Roberts CARPI, Inc. - Alberto M. Scuero/John A. Wilkes Civil & Environmental Consultants, Inc. - Chris O’Connor/Daniel P. Duffy Agru America, Inc. - Paul W. Barker/Peter Riegl Firestone Specialty Products - Paul E. Oliveira/Mark Munley Waste Management Inc. - Anthony W. Eith [BOD]/Greg Cekander GeoTesting Express - W. Allen Marr/Richard P. Stulgis [BoD] GEI Consultants - Michael A. Yako GSE Chile, S.A. - Mauricio Ossa Atarfil, S. L. - Mario Garcia Girones/Emilio Carreras Torres Republic Services Inc. - Joe Benco/Tony Walker GSE Europe - Stefan Baldauf/Catrin Tarnowski Precision Geosynthetics Laboratories - Ronald Belanger/Cora B. Queja CETCO Contracting Services - Archie Filshill Raven Industries, Inc. - Gary M. Kolbasuk [BoD] CTI and Associates, Inc. - Te-Yang Soong/Kevin Foye Advanced Earth Sciences, Inc. - Kris Khilnani/Suji Somasundaram Industries Polymex Ltda. - Cristian Valdebenito/Elias Jarufe/Enrique Saavedra Carlisle Syntec, Inc. - Randy Ober/Matt Leatherman EPI, The Liner Co. - Daniel S. Rohe/Mark Wolschon Vector Engineering, Inc. - Monte Christie Weaver Boos Consultants, Inc. - Mark Sieracke Aquatan (Pty) Ltd. - Piet Meyer PRS Mediterranean Ltd. - Arik Nagler Jones Edmunds, Inc. - Donald E. Hullings The Mannik & Smith Group, Inc. - John S. Browning III/Francis J. Biehl Plasticos Agricolas y Geomembranes, S.A.C. - Marino Gomez Montoya Afitex-Texel - Pascal Saunier EVAL Americas (Kuraray) - Robert Armstrong In-Line Plastics - Mark Williams/Don DiGuilio Bombay Textile Research Assoc. - A.N. Desai Affiliated Organizations of the Geosynthetic Institute FGSI-Korea (FITI) - Jeonhyo Kim/H.-Y. Jeon GSI-Taiwan (NPUST) - Chiwan Wayne Hsieh [BoD] Associate Members of the Geosynthetic Institute Delaware Solid Waste Authority - Anne Germain Nebraska Department of Environmental Quality - Gerald Gibson New York State Dept. of Environmental Conservation - Robert J. Phaneuf Maine Department of Environmental Protection - David E. Burns New York State Department of Transportation - Robert Burnett/James Curtis California Water Resource Control Board - Leslie Graves/Ed Wosika New Jersey Dept. of Environmental Protection - Michael J. Burlingame Pennsylvania Dept. of Environmental Protection - Steve Socash Florida Dept. of Environmental Protection - Richard B. Tedder

‐iv‐  

U.S. Bureau of Reclamation - Jay Swihart Michigan Dept. of Environmental Quality - Margie Ring/Xuede (Dan) Qian Environment Agency of the United Kingdom - Rob Marshall Florida Dept. of Transportation - Mario Paredes National Resources Conservation Center - Stephen D. Reinsch Virginia Dept. of Environmental Quality - Donald Brunson Massachusetts Dept. of Environmental Protection - Paul Emond Philadelphia Water Department - Vahe Hovsepian Oak Ridge National Laboratory (c/o Savannah River Remediation LLC) - Amit Shyan

  

The 24th Annual GRI 

Conference Proceedings  

“Optimizing Sustainability 

Using Geosynthetics” 

 

GRI‐24 Conference at the Sheraton Dallas Hotel Dallas, Texas on March 16, 2011 

 

                                                                                

 Editors: George R. Koerner  Robert M. Koerner  Marilyn V. Ashley Y. Grace Hsuan    Jamie R. Koerner

‐i‐  

FOREWORD TO THE GRI‐24 CONFERENCE  

The Geosynthetic Research Institute (GRI) is the research arm of the Geosynthetic Institute and has organized and hosted annual conferences since 1987. The first conference was one year after the institute’s founding on August 12, 1986. As such, it was meant to highlight research conducted internally as well as that of its members insofar as their own in-house R & D activities. The first thirteen conferences consisted of a single-theme and thereafter became either three or four theme events. This particular conference, however, reverts back to the original model of having a single theme, i.e., that being one based completely on sustainability. In retrospect, this theme should have been capitalized upon many years ago and perhaps at the very beginning. People in geosynthetics have always known or serious suspected that quarrying sand and gravel, traveling long distances for suitable clay soil, etc., is devastating to the environment in comparison to a comparable alternative of using geosynthetic materials; e.g., the use of geonets or geocomposites in place of granular soils, and geomembranes or geosynthetic clay liners in place of clay materials. The comparison graphic on the front of this proceedings clearly illustrates this fact in that one truckload of geosynthetic clay liners (GCL) is equivalent to approximately 150 truckloads of clay with which to make a compacted clay liner (CCL). What has changed in the intervening years since our original conference regarding sustainability is the clear-cut methodology of quantifying the differences insofar as carbon footprint between traditional and geosynthetic alternatives is concerned. Authenticated values of CO2 produced per unit weight of all construction materials are presently available through environmental agencies in both the United States, the United Kingdom and elsewhere. With these values as a benchmark, comparisons can readily be made. For example, traditional retaining walls vs. MSE walls, plastic pipe vs. concrete and metal pipe, green closure of landfills vs. traditional soil-related covers, embankment erosion protection using geosynthetics vs. concrete or rock armoring, and more are all included in these proceedings. The organization of this GRI-24 Conference on “Optimizing Sustainability Using Geosynthetics,” consists of three sessions with applications in infrastructure, drainage, and waste disposal. All twenty papers have sustainability as their focus. We, the conference organizers and proceedings editors, sincerely thank the authors and speakers for their time and effort in this regard.

  

Conference Organizers and Proceedings Editors Geosynthetic Institute 475 Kedron Avenue

Folsom, PA 19033 USA

George R. Koerner Robert M. Koerner Marilyn V. Ashley Y. Grace Hsuan Jamie R. Koerner

‐ii‐  

ACKNOWLEDGMENTS The Geosynthetic Institute (GSI) is an umbrella organization which encompasses all facets of geosynthetic materials. The five sub-institutes focus on research, education, information, accreditation and certification. A conference such as this one contains all of these activities. Clearly, research is being presented. Obviously, the effort is meant to be educational. Additionally, these proceedings form an information outlet which is available to all who are interested. Lastly, the important issues of accreditation and certification influence all of our undertakings. The institute itself is open to all organizations involved or interested in geosynthetics. This includes government (federal, state and local) agencies, facility owners, designers, consultants, testing laboratories, quality assurance organizations, resin and additive suppliers, manufacturers, manufacturer's representatives, contractors, installers, and research institutes. Recent categories of Affiliated Organizations and Associate Members have been added to facilitate international outreach and to include state regulatory agencies, respectively. Information is available on our Home Page at <www.geosynthetic-institute.org> or from the editors of these proceedings. We wish to acknowledge and thank all of the GSI members and associate members for their support of our endeavors. The current organizations (in the order in which they joined the institute) and their representatives are as follows. Current Board of Director members are identified accordingly. Full Members of the Geosynthetic Institute GSE Lining Technology, Inc. - Boyd Ramsey [BoD] AECOM - Kevin McKeon/Ken Bergschultz/John Trast U.S. Environmental Protection Agency - David A. Carson E. I. DuPont de Nemours & Co., Inc. - John L. Guglielmetti/David W. Timmons Federal Highway Administration - Silas Nichols/Daniel Alzamora Golder Associates Inc. - Mark E. Case/Jeffrey B. Fassett/Paul Sgriccia Tensar International Corporation - Joseph Cavanaugh Colbond Geosynthetics - Joseph Luna/Adrian Dobrat Geosyntec Consultants - Steve Poirier Syntec Corp. - Aigen Zhao LyondellBasell Industries - Fabio Ceccarani/Melissa Koryabina TenCate Geosynthetics - John Henderson/Chris Lawson CETCO - James T. Olsta/Tim Rafter Huesker, Inc. - Steven Lothspeich/Dimiter Alexiew NAUE GmbH & Co. KG - Georg Heerten/Kent von Maubeuge [BoD] Propex - Derek Bass/Judith Mulcay Fiberweb, Inc. - Frank Hollowell/William Walmsley/Brian H. Whitaker NTH Consultants, Ltd. - Rick Burns/Robert Sabanas TRI/Environmental Inc. - Sam R. Allen [BoD] U. S. Army Corps of Engineers - David L. Jaros [BoD] Chevron Phillips Co. - Rex L. Bobsein [BoD] URS Corp. - John C. Volk Solmax Géosynthétiques - Robert Denis

‐iii‐  

Envirosource Technologies, Inc. - Douglas E. Roberts CARPI, Inc. - Alberto M. Scuero/John A. Wilkes Civil & Environmental Consultants, Inc. - Chris O’Connor/Daniel P. Duffy Agru America, Inc. - Paul W. Barker/Peter Riegl Firestone Specialty Products - Paul E. Oliveira/Mark Munley Waste Management Inc. - Anthony W. Eith [BOD]/Greg Cekander GeoTesting Express - W. Allen Marr/Richard P. Stulgis [BoD] GEI Consultants - Michael A. Yako GSE Chile, S.A. - Mauricio Ossa Atarfil, S. L. - Mario Garcia Girones/Emilio Carreras Torres Republic Services Inc. - Joe Benco/Tony Walker GSE Europe - Stefan Baldauf/Catrin Tarnowski Precision Geosynthetics Laboratories - Ronald Belanger/Cora B. Queja CETCO Contracting Services - Archie Filshill Raven Industries, Inc. - Gary M. Kolbasuk [BoD] CTI and Associates, Inc. - Te-Yang Soong/Kevin Foye Advanced Earth Sciences, Inc. - Kris Khilnani/Suji Somasundaram Industries Polymex Ltda. - Cristian Valdebenito/Elias Jarufe/Enrique Saavedra Carlisle Syntec, Inc. - Randy Ober/Matt Leatherman EPI, The Liner Co. - Daniel S. Rohe/Mark Wolschon Vector Engineering, Inc. - Monte Christie Weaver Boos Consultants, Inc. - Mark Sieracke Aquatan (Pty) Ltd. - Piet Meyer PRS Mediterranean Ltd. - Arik Nagler Jones Edmunds, Inc. - Donald E. Hullings The Mannik & Smith Group, Inc. - John S. Browning III/Francis J. Biehl Plasticos Agricolas y Geomembranes, S.A.C. - Marino Gomez Montoya Afitex-Texel - Pascal Saunier EVAL Americas (Kuraray) - Robert Armstrong In-Line Plastics - Mark Williams/Don DiGuilio Bombay Textile Research Assoc. - A.N. Desai Affiliated Organizations of the Geosynthetic Institute FGSI-Korea (FITI) - Jeonhyo Kim/H.-Y. Jeon GSI-Taiwan (NPUST) - Chiwan Wayne Hsieh [BoD] Associate Members of the Geosynthetic Institute Delaware Solid Waste Authority - Anne Germain Nebraska Department of Environmental Quality - Gerald Gibson New York State Dept. of Environmental Conservation - Robert J. Phaneuf Maine Department of Environmental Protection - David E. Burns New York State Department of Transportation - Robert Burnett/James Curtis California Water Resource Control Board - Leslie Graves/Ed Wosika New Jersey Dept. of Environmental Protection - Michael J. Burlingame Pennsylvania Dept. of Environmental Protection - Steve Socash Florida Dept. of Environmental Protection - Richard B. Tedder

‐iv‐  

U.S. Bureau of Reclamation - Jay Swihart Michigan Dept. of Environmental Quality - Margie Ring/Xuede (Dan) Qian Environment Agency of the United Kingdom - Rob Marshall Florida Dept. of Transportation - Mario Paredes National Resources Conservation Center - Stephen D. Reinsch Virginia Dept. of Environmental Quality - Donald Brunson Massachusetts Dept. of Environmental Protection - Paul Emond Philadelphia Water Department - Vahe Hovsepian Oak Ridge National Laboratory (c/o Savannah River Remediation LLC) - Amit Shyan

‐v‐  

GRI-24 Conference Sheraton Dallas Hotel – Dallas, Texas – March 16, 2011

“Optimizing Sustainability Using Geosynthetics”

Page

Foreword i Acknowledgements ii Program v

Infrastructure Session: Moderator, George R. Koerner

1. European Perspectives on Sustainable Development Using Geosynthetics 1

Russell Jones, Golder Associates and Neil Dixon, Loughborough University 2. “Going Green” with Textile Interlayers: How to Apply with Pavement Preservation 8

John Miner, TenCate and Lita Davis, Federal Highway Administration 3. Ecological Comparison between Construction Methods with Hydraulic Binder as

well as Geosynthetics 28 Thomas A. Egloffstein, ICP Ingenieurgesellschaft mbH, Georg Heerten and Kent von Maubeuge, NAUE GmbH & Co. KG

4. A Comparison of Sustainability for Three Levee Armoring Alternatives 40 Richard A. Goodrum, Colbond, Inc.

5. Sustainability Aspects of the Fiber Reinforced Soil Repair of a Roadway Embankment 50 Garry H. Gregory, Gregory Geotechnical and Oklahoma State University

6. Reduction of Climate-Damaging Gases in Geotechnical Engineering by Use of Geosynthetics 58 Kent von Maubeuge and George Heerten, NAUE GmbH & Co. KG, and Thomas A. Egloffstein, ICP Ingenieurgesellschaft mbH

7. The Use of Nanocomposites to Improve the Physical Properties of Recycled Polyethylene 72 Archie Filshill, CETCO Contracting Services Co.

Drainage Related: Moderator, Y. Grace Hsuan

8. Carbon Emissions of Various Types of Drainage Pipes 79

George R. Koerner, Geosynthetic Institute 9. Carbon Footprint Implications of the Erosion Control Response 86

Sam R. Allen and C. Joel Sprague, TRI/Environmental, Inc. 10. Green Roofs with Geosynthetics to Optimize Sustainability 94

W. Allan Wingfield, Colbond 11. Carbon Dioxide Emission for River Dike Protection Designs in Southern Taiwan 105

Chiwan Wayne Hsieh and Jeng-Han Wu, National Pingtung University of Science and Technology and Liang-Ping Jang, Chao-Chin Hsu, and Ming-Kun Wu, 7th River Management Office, Water Resource Agency

12. Comparison of Carbon Footprints for Various Stormwater Retention Systems 111 Archie Filshill, CETCO Contracting Services Co. and Joseph Martin, Drexel University

‐vi‐  

Page

Waste Related: Moderator, Robert M. Koerner 13. The Sustainable Landfill Revisited 123

Donald E. Hullings and Hal S. Boudreau III, Jones Edmunds 14. Sustainability Contribution by MSE Berms at Landfills 133

Douglas N. Brown and Willie Liew, Tensar International Corporation 15. Carbon Footprint Comparison of GCLs and Compacted Clay Liners 142

Christos Athanassopoulos, CETCO and Richard J. Vamos, DAI Environmental Inc. 16. Geomembranes: Function and Design into Sustainable Systems and Beyond 158

Paul E. Oliveira, Firestone Specialty Products Co. 17. Reduced CO2 Emissions and Energy Consumption with Geosynthetic Installations 159

Boyd J. Ramsey, GSE Lining Technology LLC and Chris Eichelberger, American Environmental Group Ltd.

18. A True Green Closure; A Sustainable and Reliable Approach Using Structured Membrane and Synthetic Turf 163 Michael R. Ayers, Closure Turf, LLC and Jose L. Urrutia, Riley, Park, Hayden and Associates, Inc.

19. The Roles of Geomembranes in Alga Production at Landfills 172 Y. Grace Hsuan, Mira S. Olson, Richard Cairncross, Sabrina Spatari and S. Kilham, Drexel University

20. Traditional Versus Exposed Geomembrane Landfill Covers: Cost and Sustainability Perspectives 182 Robert M. Koerner, Geosynthetic Institute

‐1‐  

EUROPEAN PERSPECTIVES ON SUSTAINABLE DEVELOPMENT USING GEOSYNTHETICS Russell Jones, Principal, Golder Associates (UK) Ltd., Nottingham, UK Neil Dixon, Loughborough University, UK ABSTRACT Geosynthetics bring many benefits to civil engineering projects. Until recently, the majority of the perceived benefits were financial in nature; however increasing focus on the impact of our work on the global environment has led to the appraisal of the environmental benefits of using geosynthetics. This paper discusses the role of geosynthetics in attaining sustainable development from a European perspective. It discusses European policies on greenhouse gas emissions, assessing our carbon footprint and developing Life Cycle Assessment for civil engineering projects using geosynthetics. Finally, this paper discusses recent examples of carbon footprint reduction assessments for projects using geosynthetics. INTRODUCTION The use of geosynthetics in civil engineering applications is often found to provide financial benefits through the reduced cost of imported materials, reduced cost of wastage and generally more efficient use of resources compared with traditional solutions using soil, concrete or steel. In addition, environmental benefits are also often found where, for example, the use of geosynthetic barriers can significantly improve the performance of natural materials as barrier layers. However, there are other environmental benefits that can be obtained by the use of geosynthetics when the whole life cycle of the civil engineering project is considered. This paper presents an overview of the impact of geosynthetics on sustainable development and focuses on the view from the UK and Europe. SUSTAINABLE DEVELOPMENT The past 20 years have seen a growing realisation that the current model of development is unsustainable. In other words, we are living beyond our means. The goal of sustainable development is to enable all people throughout the world to satisfy their basic needs and enjoy a better quality of life, without compromising the quality of life of future generations. The UK government is focusing its efforts on four priority areas:

• Climate change and energy; • Natural resource protection and environmental enhancement; • Sustainable consumption and production; and • Sustainable communities.

Our ability to develop more sustainably will determine the speed and degree of climate change we experience. Whilst some climate change is inevitable due to our past greenhouse gas (GHG)

‐2‐  

emissions, we need to reduce our future GHG emissions to better manage the future impacts of climate change on the environment, economy and society. GREENHOUSE GAS CONTROL POLICIES IN THE EUROPEAN UNION Under the Kyoto Protocol, the European Union (EU) agreed to reduce GHG emissions of its 15 member states in 1997 by 8% below 1990 levels during the first commitment period of 2008 to 2012. In November 2009, the European Commission projected that it will surpass its obligation to reduce GHG emissions as the 15 member states will have reduced their domestic GHG emissions to about 7% below 1990 levels during 2008-2012 (Ref. 1). Plans by the states to acquire international credits through the Kyoto Protocol’s three market-based mechanisms would provide another 2.2% GHG reduction, while acquisitions by operators in the EU Emission Trading Systems may provide an additional 1.4% GHG reduction, and enhancement of carbon removals by sinks may offer another 1.0%. With additional policies and measures, the Commission projects that the GHG emissions may be around 13% below 1990 levels in 2008 to 2015. For the post-Kyoto period (beyond 2012), the European Council adopted on 23 April 2009 the “20-20-20 Policy” — a climate and energy package which requires by 2020:

• A 20% reduction in GHG emissions from 1990 levels; • A 20% share of renewable energy in the European Union’s final consumption figures;

and • A 20% reduction in energy consumption.

A further commitment was made to scale up the GHG emission reduction target to 30% if other developed countries make comparable efforts under a new international agreement. CARBON FOOTPRINT A carbon footprint is defined by the UK Carbon Trust as a measurement of the total GHG emissions caused directly and indirectly by a person, organisation, event or product (Ref. 2). The footprint considers all six of the Kyoto Protocol GHGs: Carbon dioxide (CO2), Methane (CH4), Nitrous oxide (N2O), Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs) and Sulphur hexafluoride (SF6). A carbon footprint is measured in tonnes of carbon dioxide equivalent (tCO2e). The carbon dioxide equivalent (CO2e) allows the different greenhouse gases to be compared on a like-for-like basis relative to one unit of CO2. CO2e is calculated by multiplying the emissions of each of the six greenhouse gases by its 100 year global warming potential (GWP). The UK Carbon Trust describes two main types of carbon footprint. Firstly, an organizational carbon footprint covers emissions from all activities across an organization which includes energy use from buildings, industrial processes and company vehicles. Secondly, a product carbon footprint covers emissions over the whole life of a product or service, from the extraction of raw materials and manufacturing right through to its use and final reuse, recycling or disposal. However, we can also consider the carbon footprint of a civil engineering structure, and this is

‐3‐  

how we can compare the sustainable development characteristics of adopting design solutions using geosynthetics with conventional non-geosynthetic solutions. Understanding the potential carbon footprint of alternative design and construction techniques is essential to allow informed selection of the most efficient civil engineering option, and to establish whether the use of geosynthetics will provide advantages over conventional, non-geosynthetic solutions. This requires a site-by-site approach which considers the nature of the project, the available materials on site and nearby, supply logistics and site layout. In the UK, a recent study was commissioned by WRAP (Waste and Resources Action Programme) to investigate the benefits of using “geosystems”, i.e. the composite working system in the ground which may, or may not, include a geosynthetic, over more traditional construction techniques using concrete and steel. The aim of the research was to assess whether geosystem-based solutions could be more sustainable than traditional designs as both concrete and steel have high levels of embodied carbon. The embodied carbon (or carbon dioxide) is a measure of the cumulative energy, and hence carbon emissions, used in the manufacture, delivery and use of materials in a civil engineering application. The embodied carbon in concrete, for example, comes from the extraction, processing and transportation of cement and aggregate constituents, together with the production of the concrete and delivery to site. The WRAP research considered the amount of embodied carbon in several civil engineering projects and compared traditional designs with designs including geosynthetic materials, and the results are presented in the WRAP report (Ref. 3). Examples given in the WRAP report are discussed further in Section 6 below. The carbon footprint of products can be calculated using the PAS 2050 methodology (Ref. 4) prepared by BSI and co-sponsored by the Carbon Trust and the Department for Environment Food, and Rural Affairs (Defra) in the UK. PAS 2050 provides a common basis for the comparison and communication of results of carbon footprint calculation. The methodology calculates those emissions released as part of the processes of creating, modifying, transporting, storing, using, providing, recycling or disposing of goods and services. The measurements can then be used to identify key sources of emissions along the supply chain which, in turn, can influence emission reduction initiatives and the development of lower carbon goods. In addition, the calculations can be used to compare civil engineering projects with and without the use of geosynthetics. LIFE CYCLE ASSESSMENT Life Cycle Assessment (LCA) is a tool for measuring the environmental impact of a product over its lifetime. LCA takes into account a product’s full life cycle; from the extraction of resources, through production, use, recycling and the disposal of remaining waste. LCA studies thereby help to avoid resolving one environmental problem while creating others. This unwanted ‘shifting of burdens’ is where you reduce the environmental impact at one point in the life cycle, only to increase it at another point. The principles and requirements of LCA are given in two ISO standards, ISO 14040:2006 and ISO 14044: 2006 (Refs. 5 and 6).

‐4‐  

The European Union recently published a guide for Life Cycle Assessment (Ref. 7) which provides technical guidance for detailed LCA studies and provides the technical basis to derive product-specific criteria, guides and simplified tools. It is based on, and conforms to, the ISO 14040 and 14044 standards. LCA studies can also be used to compare the environmental impact of two competing products or systems that can be used for some purpose. For example, two design solutions for a civil engineering project can be compared and the designer can then select the most appropriate solution based on its environmental credentials. EXAMPLES OF CARBON FOOTPRINT REDUCTION USING GEOSYNTHETICS Over the last few years, there has been an increase in the number of examples that have been published which demonstrate the reduced carbon footprint of civil engineering projects when geosynthetics have been used. The WRAP report presents six case histories of the calculation of CO2 saving for civil engineering projects. A summary of the case histories is given in Table 1 below.

Table 1 - Summary of CO2 Savings from WRAP Report

Description CO2 saving

Waste1 Fill2 Structure3 Total

1. Environmental bund Original design: Imported stone and gabion system. Geosynthetic design: Reinforced soil using on site soils.

100% 67% 96% 87%

2. Road embankment Original design: Imported stone to reduce footprint. Geosynthetic design: Reinforced soil using on site soils.

58% 36% Increase 31%

3. Retaining wall Original design: Reinforced concrete wall. Geosynthetic design: Crib wall.

73% 73% 70% 70%

4. Retaining wall

Original design: Reinforced concrete wall. Geosynthetic design: Modular block wall.

100% 100% 81% 85%

5. Retaining wall

Original design: Sheet pile wall. Geosynthetic design: Steel strip reinforced soil.

- - 84% 84%

6. Retaining wall

Original design: Hollow concrete block drainage. Geosynthetic design: Geocomposite drainage.

- Increase 82% 73%

Notes: 1. Waste material derived from the site and disposed off-site. 2. Imported material used as engineered fill on site. 3. Structural elements such as geosynthetics and conventional materials such as concrete/steel.

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Bunds and Embankments In the first WRAP case history (1, Table 1), a 100% saving in embodied CO2 for waste was achieved. This is typical in cases where the use of geosynthetic materials allows the re-use of poor on-site soils, rather than the export of soils off site, possibly to landfill. In addition to exporting soils off site, the original design required the import of virgin aggregate for granular fill. The geosynthetic solution utilised imported lime to modify the on-site fill, and so the saving in embodied CO2 is only 67%. In this case history the structural component was changed from the original gabion basket to geosynthetic reinforcement and this resulted in an embodied CO2 saving of 96%. The overall saving in embodied CO2 for this example is the highest of all six case histories at 87%. The second WRAP case history (2) comprised a road embankment which was required to have a slope gradient of 1v:2h in order to limit the footprint taken up by the structure. The original design therefore used imported crushed angular stone to form the embankment, and the disposal off-site of a significant quantity of clay material. The revised design allowed the use of the on-site clay soils to form the embankment by including geogrid reinforcement. Due to the quantities of excavation on the scheme, only a 58% reduction in embodied CO2 was achieved for the waste materials. The introduction of geosynthetic materials into the embankment resulted in an increase in embodied CO2 as no such material was to be placed in the original embankment design. However, the use of geogrid reinforcement and the re-use of on-site clays led to an overall saving in embodied CO2 of 31%. Walls The next two WRAP case histories (3 and 4) involve the replacement of reinforced concrete retaining walls with a crib wall and a modular block wall, both reinforced using geosynthetics. The first of these two case histories (3) resulted in 73% reduction in embodied CO2 for both the disposal of waste from site and the importation of suitable fill material. In addition, a reduction of 70% of the embodied CO2 was achieved by the use of geosynthetic reinforced crib wall instead of the traditional reinforced concrete retaining wall. The overall reduction in embodied CO2 for this project was 70%. In the second wall case history (4) the use of a modular block wall resulted in 100% embodied CO2 saving for both waste and fill as this design did not require any of the off-site disposal of waste and import of fill material required by the original design. This was because the original fill material was deemed to be unsuitable for use and a higher grade granular fill material was to be imported. The import of geogrid reinforcement and modular block facings instead of the steel reinforcement and concrete required by the original design, led to a reduction in embodied CO2 of 81%, leading to an overall CO2 saving of 85%. The fifth case history (5) comprised the replacement of a sheet pile retaining wall with a steel strip reinforced soil structure with pre-cast concrete panels. In this case history there was no saving in waste or imported fill material as the same quantities were required regardless of the two design options. However, a saving on embodied CO2 for the structural components of 84% was realised by the use of the revised design.

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The final WRAP case history (6) involved the drainage behind a 4m high reinforced concrete retaining wall. The original design comprised hollow concrete blocks as the drainage medium, and this was replaced by the use of drainage geocomposite. As the geocomposite was thinner than the concrete blocks, an additional quantity of fill was required to make up the difference in thickness and this led to an increase in embodied CO2. However, a saving of 82% in embodied CO2 was calculated for the replacement of the concrete drainage blocks with the drainage geocomposite which led to an overall saving of 73% of embodied CO2, despite the fact that the drainage geocomposite was delivered to the south-east of England from its manufacturing base in Germany! A different technique for comparing civil engineering projects using conventional techniques and geosynthetics was used by Heerten (Ref. 8). Heerten calculated the cumulated energy demand (CED) and CO2 emissions for both traditional reinforced concrete retaining wall and a geosynthetic reinforced retaining wall. Although the geogrid reinforced road embankment construction required around 40% more soil to be excavated, transported and placed as fill compared to the conventional wall, a reduction in CED of around 70% and CO2 emissions of around 82% was calculated for the geosynthetic solution. These reductions are in line with the values calculated in the WRAP report and confirm the significant long-term environmental benefits of using geosynthetics instead of conventional techniques. Roads A second example given by Heerten considers the design and construction of a road sub-base and compares the use of lime stabilisation with geogrid reinforcement in the soil. As only a relatively small quantity of geogrid was required for stabilisation of the sub-grade, compared with the significant quantity of imported lime, calculated reductions of CED and CO2 of 81% and 96% respectively were reported. This, again, demonstrates the significant environmental benefits of using geosynthetic solutions. CONCLUSIONS The use of geosynthetics can produce very real benefits. Not only can there be financial benefits in reduced cost of imported materials and wastage, but there may be short-term environmental and socio-economic benefits such as reduction in haulage and associated congestion, noise and air pollution. In addition, long-term environmental benefits can be achieved as LCA can demonstrate significant reduction in embodied CO2 in civil engineering projects which use geosynthetics to optimise the design. The importance and timeliness of this topic has been recognised by the UK Chapter of the IGS which is sponsoring a four year research project starting January 2011 at Loughborough University. The aim of the project is to demonstrate the low carbon credentials of geosynthetic materials in a variety of geoenvironmental and construction related applications. Appropriate use of geosynthetics can help to achieve the carbon reduction targets set by European and other international governments.

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REFERENCES 1. Europa (2009) Climate change: Progress report shows EU on track to meet or over-

achieve Kyoto emissions target, Press release IP/09/1703, 12 November 2009. 2. http://www.carbontrust.co.uk/cut-carbon-reduce-costs/calculate/carbon-

footprinting/pages/carbon-footprinting.aspx, accessed 16 January 2011. 3. WRAP (2009). Sustainable geosystems in civil engineering applications, Project Code

MRF116, May 2009. 4. BSI (2008) Specification for the assessment of the life cycle greenhouse gas emissions of

goods and services, PAS 2050:2008, ISBN 978 0 580 50978 0. 5. BS EN ISO 14040: 2006, Environmental management – Life cycle assessment –

Principles and framework, BSI, London. 6. BS EN ISO 14044: 2006, Environmental management – Life cycle assessment –

Requirements and guidance, BSI, London. 7. European Union (2010) ILCD Handbook: General guide for Life Cycle Assessment –

Detailed guidance, First Edition, Joint Research Centre, Institute for Environment and Sustainability.

8. Heerten, G. (2009) Reduction of climate-damaging gases in geotechnical engineering by use of geosynthetics, Proc. Int. Symp. on geotechnical engineering, ground improvement and geosynthetics for sustainable mitigation and adaptation to climate change including global warming, Bangkok, Thailand.

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“GOING GREEN” WITH TEXTILE INTERLAYERS: HOW TO APPLY WITH PAVEMENT PRESERVATION John Miner TenCate, Greer, SC 29650 USA Lita Davis FHWA Expert Task Group on Pavement Preservation, La Mesa, CA 91941 USA ABSTRACT

The ultimate responsibility of public agencies is to recognize they are the trustee of the

taxpayers’ money and are required to use sound engineering judgment in determining what is best, in the short term and long term, for preserving the public road system.

The current demand is to go “going green”; some practitioners address this need by

recycling materials whenever possible - in some cases this may be the best solution. Other practitioners are considering other ways to preserve the existing pavement, including material and natural resources, as another and possibly better alternative. In either case, practitioners realize the need to “go green” and are considering numerous alternatives to identify sound engineering judgments in their effort to preserve roadways.

Textile interlayers (paving fabrics) have existed since the mid-1960s and private industry

has introduced a “green paving fabric” to meet the current demand facing public agencies. Textile interlayers are recognized as a viable product and AASHTO and State DOTs have developed guidelines to assist agencies, at all levels, in its proper use and selection.

This paper will help public agencies evaluate how the use of paving fabrics (conventional

and green) can be used as a pavement preservation strategy because of its ability to address distresses in a pavement surface, and also preserve the structural integrity of a roadway. The reader will also learn how the use of paving fabrics are environmentally sensitive from manufacturing to placement, preserve material and natural resources, and are a recyclable product as well.

INTRODUCTION

Presently it is common practice for public agencies to consider recycling an existing pavement, in lieu of resurfacing. This is done in an effort to reduce demand of natural resources, energy consumption associated with resurfacing (e.g., manufacturing, hauling and placement), and placing a negative impact to the roadway’s profile and surrounding structures. However, practitioners are meeting the demand to preserve pavements by not only recycling, but by also considering other ways to preserve the existing pavement as a better alternative.

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For example, when milling of an asphalt concrete pavement is being considered, engineers evaluate the roadway’s structural section and determine how much asphalt concrete is required in order to restore or increase the structural integrity of the roadway. The pavement structure is characterized by the Structural Number (SN) expressing the structural strength of a pavement required for given combinations of soil support, total traffic expressed in equivalent single axel loads (ESAL), terminal serviceability and environment.

The thickness of asphalt concrete pavement necessary can be reduced by introducing a

paving fabric on the milled surface prior to resurfacing. The paving fabric will not only reduce the amount of asphalt concrete resurfacing required, thus saving material resources and energy consumption, but will also extend the service life of the roadway.

Agencies realize the demand to “go green” is with any construction operation. Engineers

are environmentally sensitive and are considering numerous alternatives to identify sound engineering judgments to meet this demand. Private industry is partnering in this cause as well. Industry is continuously trying to find ways to meet agencies demands and other pressures facing agencies. The National Asphalt Pavement Association identifies the following as the current incentives;

• high material costs, • high fuel costs, • increased environmental pressure, • decreased funding, and • increased traffic demands.

RECYCLYING SOFT DRINK BOTTLES THROUGH PAVING FABRICS

Conventional paving fabrics have been manufactured since the mid-1960s and are manufactured with either polypropylene or polyester. Industry has introduced a "green paving fabric" which is currently being used by agencies because of its environmental benefits. Green paving fabrics are still manufactured with polypropylene and polyester; however, its environmental benefit is the polypropylene is blended with waste polyester. The waste polyester is obtained from recycled plastic soft drink bottles.

Plastic soft drink bottles are originally manufactured from a high resin grade of polyethylene terephthalate (PET), more commonly called “polyester”. PET is one of the most commonly used consumer plastics used, thus recycling these commonly used bottles is essential. The discarded PET bottles are collected, baled and delivered to recycling plants where the bottles are then color sorted, washed, granulated and rewashed. The bottles are heated to produce a high grade of ultraviolet (UV) resistant polyester plastic pellet. The polyester pellets are then extruded and converted into a staple non-woven fiber that is used to manufacture green paving fabrics.

The green paving fabrics meet AASHTO specifications for conventional paving fabrics, including installation. Table 1 represents the life cycle of a soft drink bottle from the manufacturing of the bottle, to the recycling of the bottle into a polyester product, then into a roadway’s structural section, and the recycling of the roadway itself.

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Green paving fabrics contain over 25 percent of post-consumer waste as defined by Leadership in Energy and Environmental for New Construction (LEED), primarily obtained from recycled plastic soft drink containers; 90 percent of these bottles are collected from landfill sites. The increased number of containers recycled by consumers would increase the recovery of bottles that are sold.

Table 1 – The Life Cycle of a Soft Drink Bottle

CONVENTIONAL AND GREEN PAVING FABRICS What is the Difference between Conventional and Green Paving Fabrics?

Conventional paving fabrics have been around since the mid-1960s. The manufacturing process begins with a pelletized chip of polypropylene or polyester resin that is extruded into fiber and processed through a carding system with needling (needle punching) to follow, or a spun-bonded process. The fabric is then heated on one side as a constructability benefit for applying to pavements.

In contrast, green paving fabrics use the extruded fiber from the polypropylene process

and blend the extruded fiber with a polyester fiber from a recycler. The fibers are then processed through the carding system which requires some adjustment prior to needling (needle punching). The heating application is altered in order to provide constructability for applying to pavements.

The recent development of the green paving fabric is an example of how industry

addresses the ongoing needs of public works agencies – develop a product that preserves natural resources by not only manufacturing the fabric from recycled products, but saves natural resources over other methods used to preserve roadways, and is recyclable itself.

Green paving fabrics also meet the standards set for the Comprehensive Procurement

Guidelines Program, Office of Resource Conservation and Recovery (5306P) U.S. Environmental Protection Agency by providing a minimum of 25 percent post consumer waste of materials used in the product.

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The installation process for green paving fabric is the same for a conventional paving fabric. Successful installations have occurred in the field including with the increased amount of liquid paving asphalt (fabric binder); see Figure 1.

Figure 1. Green paving fabric being placed in Maryland.

GREEN ATTRIBUTES OF CONVENTIONAL PAVING FABRICS Manufacturing Savings

Savings are realized in the manufacturing of paving fabrics because most manufacturers recycle 10 percent of post industrial waste when manufacturing conventional paving fabric – the 10 percent recycled is allowed under Leadership in Energy and Environmental for New Construction Design (LEED) MR 4.1. The recycled post industrial waste is graded by strict quality control measures and is extruded into fiber which is a needed component for the manufacturing of paving fabrics.

BTU Savings

Paving fabric interlayers have successfully been used in the United States, and contributed to the environment, for over 40 years and have made a significant contribution to the environment by reducing the need for energy (BTUs) to produce, transport and place hot-mixed asphalt concrete (HMAC) used to maintain roadways. Jim Dykes reported in Phillips 66 Paving Information Bulletin Number 110, that the use of a paving fabric with a HMAC overlay will save 1,170,709,700 BTU/mile. This is possible because the use of paving fabrics reduces the required thickness of HMAC required to resurface a roadway. By reducing the quantity of HMAC to resurface a roadway, BTU savings are realized with the production, transport and placement of HMAC needed to resurface the roadway.

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Materials Savings

In December 1997, Maxim Technologies, Inc. of Austin, Texas did a study of the structural requirements for resurfacing a pavement with asphalt concrete pavement, with or without a paving fabric interlayer; Table 2 reflects those findings. This study shows that, depending on the proposed thickness to resurface a roadway, incorporating a paving fabric interlayer can reduce the proposed thickness as shown in Table 2. The incorporation of a paving fabric interlayer will also reduce the amount of HMAC resurfacing required to address reflective cracking from the underlying pavement.

Table 2 – Structural Requirements in Dry and Wet Environments

Dry Environment

Existing AC

(Inch)

Proposed AC Thickness Without Fabric

(Inch)

Proposed AC Thickness With Fabric

(Inch)

Reduction In

AC Thickness (Inch)

2.00

4.50 2.50 1.75 3.50 2.38 1.12 2.50 2.00 0.50

3.00

4.50 3.00 1.50 3.50 2.50 1.00 2.50 2.00 0.50

4.00

4.50 3.25 1.25 3.50 2.62 0.88 2.50 2.00 0.50

Wet EnvironmentExisting AC

(Inch) Proposed

AC Thickness Without Fabric

(Inch)

Proposed AC Thickness With Fabric

(Inch)

Reduction In

AC Thickness (Inch)

` 2.00

4.50 3.12 1.38 3.50 2.62 0.88 2.50 2.00 0.50

3.00

4.50 3.25 1.25 3.50 2.12 1.38 2.50 2.00 0.50

4.00

4.50 3.50 1.00 3.50 3.25 0.25 2.50 2.00 0.50

Another benefit of paving fabric is to lower the permeability of an asphalt concrete

pavement by reducing the amount of water entering the road base via the pavement surface. When paving fabrics are used to keep water from the road base this equates, at a minimum, of good to excellent AASHTO drainage classification. Because there is limited water dwell time in

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the road base, a structural credit used for improved drainage can be applied to the drainage reduction coefficient of 1.0 to 1.3.

When the existing pavement is structurally sound and the design considerations are

primarily to delay reflective cracking, a paving fabric interlayer becomes an obvious consideration because the paving fabric will delay reflective cracking when placed with as little as 1.5 inch of HMAC. As a result, a savings in the quantity of natural resources needed to produce HMAC.

According to the National Asphalt Pavement Association (NAPA), there are two basic

ingredients in HMAC. The first is aggregates (crushed stone, gravel, and sand). The aggregates used are almost always locally available stone and account for approximately 95 percent of the total weight of an asphalt pavement. The remaining five percent is asphalt cement. Using these percentages, and 145 pounds per cubic foot for HMAC, the following savings can be realized with the reduced amount of HMAC required when combined with a paving fabric interlayer; see Table 3.

Table 3 – Savings in Aggregates and Asphalt Cement

Existing AC

(Inch)

Proposed AC

Thickness Without Fabric (Inch)

Proposed AC

Thickness With

Fabric (Inch)

AC Thickness Reduction

(Inch)

Aggregate Savings Per Lane Mile

(Ton)

Asphalt Cement

Savings Per Lane Mile

(Ton)

2.00

4.50 2.50 1.75 636 33 3.50 2.38 1.12 407 21 2.50 2.00 0.5 182 10

3.00

4.50 3.00 1.5 545 29 3.50 2.50 1 364 19 2.50 2.00 0.5 182 10

4.00

4.50 3.25 1.25 455 24 3.50 2.62 0.88 320 17 2.50 2.00 0.5 182 10

DELAY OF REFLECTIVE CRACKING

Paving fabric interlayers have been in existence for decades and advancements are continually being made to meet the needs of public works agencies. Presently, there are many pavement preservation strategies involving paving fabric interlayers which are reducing the cost to maintain or rehabilitate pavements. As shown in the following figures, both laboratory and field testing have proven that a paving fabric interlayer system is effective in delaying reflective cracking in an asphalt pavement, see Figures 2 and 3.

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Figure 2. Beam testing in 2008, Asphalt Technologies, Inc. Testing Laboratory, Florida

Figure 3. Overlay testing in 20008, Texas Transportation Institute REVIEW OF DATA SUPPORTING WATER CONTROL BENEFITS

Pavement engineers agree there is a need to reduce a pavement’s exposure to surface water penetration because prolonged exposure is harmful to the roadway’s structural section and can reduce the bearing capacity of a loaded pavement. There are concerns which design method is best to limit and control a pavement’s exposure to surface water.

Pavement engineers need to evaluate a roadway’s demographics, identify the various

design options in constructing or maintaining a pavement, and evaluate the risks and benefits of each design before making a final selection. In evaluation of a paving fabric as a moisture barrier, basic principles apply to both the use in new roadways and pavement resurfacing.

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When designing a new roadway, the consideration of handling water flow and runoff will determine the applicability of a paving fabric as a moisture barrier.

There is a difficulty in measuring permeability in the laboratory and achieving a direct correlation of water flow in pavements, and the damage caused to the pavement or the road base. Studies have included the permeability of a paving fabric when saturated with liquid asphalt - these studies addressed the paving fabric’s saturated state and testing between the asphalt layers. Testing was also done on field samples of asphalt with and without cracks. Studies were performed in the laboratory and in the field on the effectiveness of the paving fabric. These studies confirmed that the use of paving fabrics do lower the permeability of asphalt pavements and reduce the amount of water entering into the road base.

An important benefit of a nonwoven paving fabric is that it is an effective moisture barrier throughout the life of the pavement. This is possible because the asphalt saturated paving fabric will continue to perform as a moisture barrier during the ageing process of the pavement because of its ability to flex within the asphalt concrete pavement. The asphalt saturated paving fabric will continue to provide waterproofing benefits even when the pavement is resurfaced with future asphalt overlays or even surface treatments, such as chip seals. Therefore, it is beneficial to an agency to utilize paving fabrics early in the life of the pavement to realize the benefits of an effective moisture barrier.

Studies were performed in the field and laboratory to evaluate the reduction of water percolation through a pavement where a paving fabric was used. Some studies used asphalt core samples from roadways, and others used laboratory prepared samples. These studies consistently showed that the presence of a paving fabric interlayer system reduces water percolation through asphalt concrete pavements. Other observations show that where cracks do reflect through the resurfacing material (asphalt concrete or chip seal), the paving fabric will stay intact and continue to provide a waterproofing moisture barrier. The following testing was done to support this evaluation.

Field Testing Los Angeles County Permeability Test Results

In 1994, Los Angeles County performed falling head permeability tests on 4-inch cores from Olympic Boulevard with the following results: Cores with a rubber asphalt content of 7.6 percent resulted in a permeability of about 10-1 to 10-3 mm/sec, depending on the degree of compaction. Permeability on highly compacted asphalt cores using 5.6% AR4000 liquid tack coat generated results of 10-4 mm/sec. Cores containing paving fabric with AR4000 liquid tack coat resulted in a permeability of 10-5 mm/sec.

Texas

In a 1989 study in Texas, test sections consisting of HMAC over paving fabric was examined and compared to control sections, to determine moisture related improvements associated with the paving fabric interlayer system. At a section near Amarillo, five different

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paving fabrics as well as control sections for comparison were installed. After rains, sections containing paving fabric exhibited less pumping deformation than control sections. This implies that the subgrade support was better in the paving fabric sections due to lower base and subgrade moisture content than in the control sections. This waterproofing benefit was still realized even after some cracking appeared on the surface of the thin asphalt concrete resurfacing treatment.

Oklahoma

In 1996, a study was performed by Oklahoma DOT to evaluate the effectiveness of drainable bases and edge drain systems when using paving fabric interlayers. Five pavement sections were monitored for approximately three years. The five sections of pavement had varying degrees of permeable bases and had some differences in edge drain systems.

In 1997, Oklahoma DOT returned to this site to determine why water was not draining

from the pavement. In their investigation, they cored through the paving fabric interlayer system to the top of the break-and-seat base layer. A percolation flow test was then run by pumping water into the core to see if it would flow to the edge drain system. The water did flow and the break-and-seat base was determined to have an AASHTO drainage capacity of “good”. Therefore, since the base was drainable, the most probable reason that water was not flowing from the pavement after a rain was because the paving fabric interlayer system was restricting water infiltration from reaching the road base.

When a properly installed paving fabric interlayer system keeps the water from the road’s

base, this equates to at least the “good to excellent” AASHTO drainage classification since there is limited water dwell time in the road base. Therefore, it is reasonable to apply a structural credit, normally used for improved drainage, where a paving fabric interlayer system is used.

Georgia

Georgia DOT evaluated a four-year old installation of HMAC overlay over paving fabric on Highway I-85. A six-inch diameter core sample was removed and tested to determine the amount of water that could penetrate through the paving fabric. The core was subjected to a three-inch head of water for 16 hours; test results showed there was less than 10 percent of water that penetrated through the paving fabric.

California

The State of California Department of Transportation (Caltrans) constructed control and test section to determine the permeability of cracked asphalt concrete resurfacing placed over paving fabric (Caltrans Memorandum, May 8, 1984).

Test Site: 03-PLA-80-31.33/33.18, Colfax. Field data and cores for this investigation

were obtained. Test sections were placed in July 1974 over an asphalt concrete roadway that was built in 1959. The original structural section consisted of 0.30-feet HMAC over 0.67-feet cement treated base over 0.67-feet aggregate base.

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Asphalt concrete resurfacing occurred July 1974 and cores were taken March 1984. The results of the permeability testing are shown in Table 4.

Table 4 – Results of Permeability Testing

Core No. Core Type Vacuum

Permeability ml/100 sec. 4 Control 2.75 5 Control 8.25 6 Paving Fabric 0.00 7 Paving Fabric 0.00 8 Paving Fabric 0.00 9 Paving Fabric 0.00 10 Paving Fabric 0.04 11 Paving Fabric 0.00 12 Control 0.00

Laboratory Testing

Laboratory testing, for these purposes, is defined as testing with laboratory prepared hot mix samples, using various paving fabrics. The permeability advantage of paving fabrics in the laboratory is confirmed by Asphalt Technologies, Inc., Phillips Petroleum and PRI.

PRI 2008 Study

The objective of PRI Study of 2008 was to determine hydraulic conductivity according ASTM D5084 on select core samples with and without cracks, and with and without paving fabric (TRB Circular #E-C006).

The sample cores were prepared by coring from the beam on elastic foundation slabs

prepared for reflective crack testing at the crack, and away from the crack. As a result of this test, cracking is very slight and represents the beginning of the cracking process. The hydraulic conductivity of the control sample with a crack was one order of magnitude higher than the paving fabric sample with a crack; see Table 5.

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Table 5 – PRI 2008 Study on Hydraulic Conductivity

Property ASTM

Test Method

Results - Core ID Control

No Crack Control

With Crack Fabric

No Crack Fabric

With Crack Core Weight,

grams

D3549

1,320.4 1,336.9 1,371.1 1351.5

Core Diameter, 0.1-inch 3.98 3.98 3.97 3.97

Core Thickness, 0.1-inch 2.6 2.6 2.7 2.7

Hydraulic Conductivity,

m/s D5084 1.59x10-9 2.43 x10-5 1.16x-7 2.25x10-6

Testing of Asphalt Saturation

Phillips Fibers Corp (Phillips Petroleum Co.) conducted studies to evaluate a paving fabric interlayer as a waterproofing membrane. Conclusion from the studies confirmed the success of a paving fabric interlayer system is dependent on proper installation.

The manufacturer’s installation guide recommends a tack coat application rate of 0.25

gallons per square yard. This is consistent with studies that show very little improvement in waterproofing can be expected until the tack coat is applied above 0.21 gallon per square yard. When tack coat levels are above 0.23 gallons per square yard, the paving fabric starts to achieve permeability of 10-5cm/seconds or less which will greatly enhance the waterproofing of a pavement; see Table 6.

Table 6 – Evaluation of a Paving Fabric Interlayer as a Waterproofing Membrane

(Summations from TBR Circular #E-C006)

APPLICATIONS AND LIMITATIONS

The use of a conventional paving fabric or the new evolutionary green paving fabric can be used to extend the life of a pavement and can be applied using current pavement design criteria. The development of design thickness includes wheel loading, existing pavement

Residual Asphalt

(gal/yd2)

Flow of Water 3-Inch Head

(ml/900 seconds) 0 7,290

0.15 759 0.2 28.3 0.25 0

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strength, drainage and climatic conditions. Available data supports the use of paving fabrics when the manufacturer’s recommendations for fabric selection and application are followed.

The important properties of a paving fabric are weight, tensile strength, elongation and asphalt retention. Paving fabrics retain the applied liquid paving asphalt tack coat, and this combination results in a paving fabric interlayer system. Predominate fabrics used today are categorized as Light Duty, Standard or Heavy Duty. The properties for each category of paving fabric are identified by AASHTO designation in Table 7.

Table 7 – AASHTO Designations for Paving Fabrics

Industry has categorized paving fabrics as follows:

• Light duty paving fabrics are used in low-volume pavement in moderate climate and with slight distress. Used with HMAC or chip seals.

• Standard paving fabrics are the current AASHTO M288 specified in most state and local agency projects. Used with HMAC or chip seals.

• Heavy duty paving fabrics are those that exceed the AASHTO M288 specification and are recommended for severe pavement distress, heavy wheel loading and harsh climatic conditions. Used with HMAC.

When specifying a “green paving fabric”, the above requirements must include that the fabric consists of a post consumer waste greater than 25 percent as calculated by LEED. Climate Considerations and Fabric Selection

Paving fabrics interlayers are effective in most, but not all, climates of the United States. Laboratory and field testing has improved guidelines on the proper selection of a paving fabric which is dependent on the annual temperatures and roadway conditions.

Specification Light Duty AASHTO M288-92

Standard AASHTO M288-00

Heavy Duty AASHTO M288-97

Fabric Property

ASTM Test

Method Unit Mass Per Unit Area D5261 ounce/yd2 3.5 4.1 6

Grab Tensile

D4632 pounds 90 102 150

Grab Elongation D4632 % 50 50 50

Mullen Burst

D3786 pounds/in2 180 200 290

Asphalt Retention D6140 gal/yd2 0.2 0.23 0.3

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General recommendations include Light Duty paving fabrics for warm and tropical regions with extreme variation with light traffic. Standard paving fabrics are best used in warm, tropical and moderate to severe climates. Heavy Duty paving fabrics are recommended in severe climates. In moderate climate areas, the paving fabric selected is not as critical as those considered for use in more severe climate conditions. Cold climates require more consideration for proper selection of the paving fabric including evaluation of the pavement, and the hot mix asphalt overlay intended for use.

Fabric selection is based on the annual low ambient temperatures, over a three-month

average, in the climate area considered for use. Climatic regions where paving fabrics are used successfully are shown in Table 8.

Table 8 – Climate Fabric Zones for Paving Fabrics Based on Three-Month Average Low

Temperature

Challenges

Experience has shown that reflective cracking caused by vertical and or horizontal movements in a pavement, due to extreme freeze-thaw conditions, provides a difficult challenge. The greater the temperature differential, this phenomenon accelerates the rate of crack growth in the existing pavement and new asphalt concrete overlay.

Freeze-thaw cycles cause the expansion and contraction of frozen water within the

pavement and the roadway structural section. This situation warrants special consideration for asphalt pavement overlays including mix design, overlay thickness and asphalt binder.

Damage to the roadbed is accelerated when water is able to be present within the

roadway structural section. When this occurs, common results are quick and severe fracturing of the pavement. In most cases, a paving fabric may not stop these thermal cracks from propagating through the pavement. However, paving fabrics have proven their ability to delay the cracking of the asphalt concrete pavement surface and also to minimize damage to the roadway structural section by greatly reducing water infiltration from the pavement surface.

Heavy duty paving fabrics should be considered for cold climatic conditions. Laboratory

and field evidence has shown that since a thicker paving fabric requires a higher application of liquid paving asphalt as a binder, then a greater amount of liquid paving asphalt is saturating the paving fabric. As such, this is a benefit over Light Duty or Standard paving fabrics because the

Climate Zone Three-Month Average Low Temperature

Fabric Type

Warm >42°F (>6°C) Light Duty or Standard Moderate >24°F (>4°C) Standard Cold >15°F (>-9°C) Heavy Duty Severe <15°F (<-9°C) Not Recommended

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Heavy Duty paving fabric being saturated with a greater amount of liquid paving asphalt increases its ability to blunt the crack tip stress and enhance its waterproofing capabilities.

Modified Tack Coats

Success has also been demonstrated with the use of polymer modified liquid asphalt binder and a Heavy Duty fabric in cold climatic conditions. Test results confirm that polymer modified liquid asphalt adds strength at a lower elongation with high and low temperature ranges when applied with a paving fabric. The polymer modified liquid asphalt-paving fabric interlayer system has been used with PG 76-22 in several projects in the Chicago area.

The oldest site was built in June 2002 on a heavily traveled arterial in the industrial area

of Libertyville Township. The existing pavement had an estimated PCI of 10, on a scale of 100. Full-depth asphalt patching was required for 40 percent of the arterial and the Township opted for a less expensive solution. The final design was to mill 2 inches and fill with a 3/4-inch leveling course, apply a heavy-duty paving fabric (6 ounce), then overlay with PG 76-22 asphalt consisting of a 2-inch binder course and a 1-1/5 inch surface course.

USING PAVING FABRICS TO MAINTAIN PAVEMENTS Maintaining Rigid Pavements

The presence of cracks or joints in a portland cement concrete (rigid) pavement can be a problem if a HMAC (flexible) overlay is placed in order to improve serviceability. This is true when the cracked or jointed rigid pavement is subject to temperature drops that cause the rigid slabs to have a rocking action. The slabs rock as the traffic load transfer from one end of the rigid slab to the other.

Rigid slabs are often resurfaced with HMAC. HMAC pavements are flexible, but often

are not flexible enough to bridge the upward and downward movement of the underlying rocking slab. The rocking action will cause the cracks or joints in the underlying rigid pavement to travel upward and through the flexible pavement. When the cracks reach the flexible pavement surface, this allows water to penetrate to the roadway’s structural section.

Designs in severe climatic conditions require an increased HMAC thickness as a

mechanism for bridging the expansion and contraction of thermal joints. Designing for this condition is not used as often as it should be, primarily for economic reasons. Paving fabrics are not recommended for this application; however, if a thin HMAC overlay is the only alternative a Heavy Duty fabric may be used.

Caltrans “crack-and-seat” procedure is one of the most effective methods used to extend

the serviceability of a rigid roadway by placing a flexible pavement over a rigid pavement. This method typically uses a Standard paving fabric beneath the flexible pavement, but able the cracked-and-seated rigid pavement, in an effort to address reflective cracking and provide a waterproofing moisture barrier.

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Maintaining Flexible Pavements Paving fabrics can be used to effectively reduce reflective cracks and provide a

waterproofing mechanism for flexible pavements. Paving fabrics are not designed to correct a structurally inadequate designed structural section or overlay. Proper design is always required to determine the structural requirements for a new roadway, as well as resurfacing of an existing roadway. It is important to remember the design purpose and benefits of a particular paving fabric, and design accordingly. Paving fabrics are designed to be saturated with liquid paving asphalt, such as performance grade liquid asphalt, and are most effective for the following pavement conditions:

Block and Alligator Cracking

Paving fabrics are effective in addressing block cracking and slight to moderate alligator cracking on an asphalt surface; see Figures 4 and 5.

Light Duty paving fabrics is commonly sued for less severe or slight alligator cracking on

roads with less than 5,000 ADT. Heavy Duty paving fabrics can be used for slight to severe alligator or block cracking

where the asphalt pavement is intact and not loose. In these cases, the Heavy Duty paving fabric should be covered with a minimum of 2 inches of HMAC.

Figure 4. Paving fabric usage and alligator cracking.

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Figure 5. Paving fabric usage with block cracking.

Oxidized Pavement Surfaces

Light Duty and Standard paving fabrics are the most economical paving fabric for oxidized or aged pavements. A minimum of 1.5 inches of compacted HMAC is required when placing over paving fabric. This method has proven to be an effective surface treatment in milder climates. Light Duty and Standard paving fabrics are also an excellent choice when placed prior to a single or double-chip seal. Such methods have been found successful for over 20 years on low and high speed roadways with less than 10,000 ADT.

RECYCLING PAVING FABRICS

Phillips Petroleum has proven that paving fabrics can be recycled when incorporated with hot mix asphalt concrete (HMAC). The current view of recycling of HMAC with paving fabric is that it is a difficult process – this is only true if the paving fabric is placed improperly or if improper recycling methods are utilized. This analogy is true with any construction process, i.e., use the proper tools and methodology to obtain the desired end product.

The current process of installing paving fabric has improved with knowledgeable

agencies, contractors and fabric installers by using improved computer rate controlled distributor trucks to apply the fabric binder. This is done to insure the proper amount of performance graded (PG) asphalt binder is being placed to obtain the waterproofing benefit of the installed paving fabric, and insure enough binder is also present to allow adhesion of the HMAC resurfacing to the paving fabric and to the underlying pavement.

Milling of a HMAC pavement with a paving fabric interlayer present can be done if the

appropriate milling equipment and technique is used. Milled HMAC with paving fabric can be processed through asphalt plants and recyclers that have the resources to effectively process these milled materials - these facilities are able to process these milled materials in large quantities. The following summarizes the successful recycling of conventional paving fabrics:

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• Apply the proper amount of PG asphalt binder when placing paving fabric to insure adhesion of the HMAC to the paving fabric, and the paving fabric to the underlying pavement

• Use appropriate milling equipment and milling techniques • Process milled material through asphalt plants or recyclers properly equipped to process

properly milled HMAC with paving fabric

Green paving fabrics will give some improvement over conventional paving fabrics because of its blended construction. Green paving fabrics are expected to have a higher effectiveness as a waterproofing barrier because of its increased amount of PG asphalt binder applied during placement. The increased amount of PG asphalt binder retained, and its manufacturing with PET fiber properties, will be a benefit in its recyclability.

When is it Beneficial Not to Recycle the Paving Fabric Interlayer?

Users of paving fabrics with HMAC realize that paving fabrics provide the following benefits: controls reflective cracking, prevents surface water infiltration, stabilizes subgrade moisture content, allows wet subgrades to regain strength and load-carrying capacity, and extends the service life of a pavement.

When it is necessary to mill a HMAC pavement that has a paving fabric present, careful

consideration should be done as whether or not to mill the paving fabric interlayer. Milling the paving fabric will remove the waterproofing benefits it provides and pavement distress may once again occur when the pavement is replaced without a paving fabric. As such, those that use paving fabrics realize the long-term benefits paving fabrics provide and are allowing the paving fabric to remain in the roadway. If the structural integrity of the roadway allows, practitioners are milling above the paving fabric interlayer in order to keep the waterproofing barrier and stress relief in place, and continue to perform, with the newly placed road surface.

LIFE CYCLE COST BENEFITS

The relative life cycle cost of placing paving fabrics with asphalt overlays, when considered to other types of rehabilitation processes, is truly an economical method in addressing a roadway’s maintenance needs. Pavement preservation practitioners have also found the same benefits can be realized when paving fabrics are used with a surface treatment, such as chip sealing.

FHWA policy supports the fact that life cycle cost analysis (LCCA) is a decision support tool. As a result, the use of LCCA is encouraged in analyzing all investment decisions. Dr. Hicks and Dr. Epps, reported that LCCA should be conducted early in the project development cycle as possible and that the level of detail in the analysis should be consistent with the level of investment. The current and future benefits realized from using paving fabrics are two of the steps that should be considered in the LCCA. Some of these benefits are;

• extension of a roadway’s service life, • reduction in subsequent roadway maintenance needs (e.g., crack filling, crack sealing

or pothole repairs), • reduction in traffic disruption associated with road maintenance, and

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• reduced energy used to produce and place hot mix asphalt concrete or performance roadway maintenance operations.

Life cycle costing for paving fabric with asphalt concrete overlays has been documented

from field results of actual fabric installations. Caltrans developed the early data for cost savings and gave a value of 1.2 inches for paving fabric for the purpose of reflective cracking when used with asphalt concrete overlays.

In 1997, TRI Environmental, Inc. conducted a study to evaluate the most cost effective

solutions for pavement maintenance in Greenville County, South Carolina. The study reviewed pavement condition index (PCI) records over a 15 year period. A review of the PCI revealed that when pavement conditions were between 10 and 30, reconstruction was the most cost effective solution. When the PCI was between 30 and 50, the most cost effective solution was an asphalt concrete overlay over paving fabric. When the PCI was above 50, an asphalt concrete overlay with or without paving fabric was about equal.

This study showed the maintenance options that were considered when a roadway had a

PCI level of 40 the most economical treatment was an asphalt concrete overlay over paving fabric. The prices shown below are from the 1997 study, and do not reflect current prices:

• $0.20/yd2 for cold mill recycling • $0.16/yd2 for asphalt concrete overlay • $0.11/yd2 for an asphalt concrete overlay with paving fabric

In 1997, Maxim Technologies reported that there is a consensus of opinion among

literature searched and experts interviewed, that the addition of a paving fabric gives additional overlay performance equivalency of approximately 1.3 inches of asphalt concrete hot mix – assuming that the existing pavement, including the structural section, is stable.

SUMMARY

The ultimate responsibility of public agencies is to recognize they are trustees of the taxpayers’ money and are required to use sound engineering judgment in determining what is best in the short term, and long term, when maintaining or rehabilitating public roadways. This paper should help public agencies accomplish this task.

Textile interlayers can now be manufactured with the use of post consumer waste, which

with conventional paving fabric are recyclable and can assist practitioners in their efforts to preserve flexible and rigid pavements and “go green”.

In 2007 at the Hot Mix Asphalt Energy and Recycling Symposium, the keynote

presentation made a statement that applies to public and private industries alike; “We must have the will to educate ourselves and the courage to innovate new solutions if we are to provide the transportation system our country needs to maintain economic leadership.” The incorporation of paving fabric interlayers is a valuable tool in preserving our natural resources, reducing energy

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consumption, maintaining our country’s transportation system with the economic diligence entrusted to us all from our constituents, the public taxpayer.

BIBLIOGRAPHY Al-Qadi, I. (1997). Petromat Evaluation in Kernersville, North Carolina. Virginia Polytechnic Institute Barksdale, Richard D. (1991). Fabrics in Asphalt Overlays and Pavement Maintenance. TRB Research Synthesis 171. Davis, L. (2003). “Protecting Roads in the Desert – Chip Sealing over Fabric Retards Reflective Surface Cracks”, TR News 228, 14-15. Federal Register September 20, 1995 (Updated January 28, 2009). Wastes-Resource Conservation-Comprehensive Procurement Guidelines. Forsyth, R.A., Doty, R.N. and Smith, R.D. (1984). Laboratory Testing of Fabric Interlayers for Asphalt Concrete Paving (Final Report). Caltrans Division of Engineering Services Office of Transportation Laboratory in cooperation of FHWA . Contract # F78TL03. Fujian Ni, Yingmei, Yin and Xingyu Gu (2005). Study on the Fatigue Properties Asphalt Mixtures with Fiberglass/Polyester Mat Reinforcements, Transportation Research Circular 05-5555. Guram, S.S. (1983). Evaluation of Petromat as a Waterproof Membrane. Internal Memorandum, Phillips Petroleum Co. Hicks, R. Gary and Epps, Jon A. Life Cycle Cost Analysis of Asphalt-Rubber Paving Materials. Hughes, C.S. (1977). Minimization of Reflection Crack in Flexible Pavements. Virginia Department of Highways and Transportation and the University of Virginia. Marienfield, M.L. and Baker T.L. (19699). Paving Fabric Interlayer System as a Pavement Moisture Barrier. Transportation Research Circular E-C006. Maximum Technologies, Inc. (1997). Nonwoven Paving Fabrics Study. Miner, J. L. (1985). Fabrics in Pavement Maintenance. APWA Workshop on Pavement Maintenance Practices. Monismith, C. L. and Deacon, J. A. (1969). Fatigue of Asphalt Pavement Mixtures. Journal of Transportation Division, A.S.C.E., No TE 2.

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Monismith, C.L. and Long, F. (1999). Overlay Design for Cracked and Seated Portland Cement Concrete ( PCC) Pavement – Interstate Route 710. Technical Memorandum TM UCB PRC 99-3 Prepared for Long Life Pavement Task Force, University of California, Berkeley. National Association for PET Container Resources. (2007). Report on Post Consumer PET Container Recycling Activity (Final Report). Pourkhosrow, G. and Hixon, C. D. (1982). The Evaluation of Non-Woven Fabrics: Petromat and Mirafi. Research and Development, Oklahoma Department of Transportation Rowe, G.M., Lewandowski, L.H, Grzybowski, K.F., and Rasche, J. (2008). Development of the Beam on Elastic Foundation for Evaluation of Geo-Synthetic Materials for Reinforcing of Asphalt Layers. Transportation Research Board. Sprague, C.J., (2006). Study of the Cost-Effectiveness of Various Flexible Pavement Maintenance Treatments, Transportation Research Circular E-C098. U.S. Green Building Council. (2009). MR Credit 4: Recycled Content, LEED 2009 for New Construction and Major Renovations.

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ECOLOGICAL COMPARISON BETWEEN CONSTRUCTION METHODS WITH HYDRAULIC BINDER AS WELL AS GEOSYNTHETICS

Thomas A. Egloffstein, ICP Ingenieurgesellschaft mbH, Karlsruhe, Germany Georg Heerten, Naue GmbH & Co.KG, Espelkamp, Germany Kent von Maubeuge, Naue GmbH & Co.KG, Espelkamp, Germany

ABSTRACT

This article will conduct a comparison between classical construction methods from earthwork, foundation engineering and geosynthetic construction methods with the help of actual examples and taking into account the cumulated energy demand (CED) for primary, intermediate and finished products, their transport to the manufacturer and the construction site as well as their installation.

The climate related CO2 emission and other pollution gases have been taken into account in addition to the CED.

For the example “lime, cement, reinforced concrete versus geogrid“ a clear advantage of the geogrid solution compared to the use of lime (also lime hydrate, cement, subbase binder) became apparent, indicating a considerably smaller CED and CO2 emission. The basic causes for this result are the very small amounts of geosynthetics from polypropylene (PP) required, besides the high specific CED and CO2 emission per kg PP.

INTRODUCTION

A Life Cycle Assessment (LCA) denotes the systematic analysis of the environmental impact of products during their entire life cycle (extraction and treatment of raw materials, pro-duction, distribution and transport, use, consumption and disposal). This comprises any envi-ronmental impact during the production, utilization phase and disposal of the product as well as the upstream and downstream processes connected to that (e.g. production of raw and process materials). Environmental impact may include any ecologically relevant extraction from the en-vironment (e.g. raw oil, soil, ore), as well as emission into the environment (e.g. waste, carbon dioxide emissions).

It is generally distinguished between:

● a life cycle assessment taking into account the environmental impact of an individual product, ● a comparative life cycle assessment pursuing a confrontation of several products, as well as ● an integral account, embracing the economical, technical and / or social aspects.

Figure 1 shows the phases of a life cycle assessment and the correlation between the terms life cycle inventory analysis, impact balance or impact assessment, respectively, and eval-uation. Direct applications of life cycle assessments comprise for instance the development and

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improvement of products, strategic planning, political decision making processes or marketing etc.

Figure 1 - Constituents of a life cycle assessment (pursuant to DIN EN ISO 14040 2006-10 / 14044, 2006-10) and definition of the term environmental audit.

EXPLANATIONS CONCERNING LIFE CYCLE ASSESSMENT, INVENTORY ANAL-YSIS AND IMPACT BALANCE, SCOPE OF ASSESSMENT AND CUMULATED EN-ERGY DEMAND (CED)

Procedure

1. Determination of the objective and scope of assessment (scoping) Determination of the framework, identification of the scope of assessment (planning tar-get), justification of the priority setting, determination of balance scope and balance crite-ria

2. Life cycle inventory analysis – account of the material and energy flows

3. Impact analysis and evaluation including the determination of environmental goals of overriding importance

4. Optimisation

Method for the compilation of an impact balance

In the interest of a subsequent, possibly comprehensive evaluation it is reasonable to con-duct an impact related account between the individual life cycle inventory analysis and the eval-uation of the balance. The flow and inventory parameters collected in the life cycle inventory analysis are described or assessed, respectively, with regard to their potential effects. Their im-pact on selected global and regional or local environmental factors is considered. The effects

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from the life cycle inventory analysis may be analysed with regard to the following environmen-tal categories (SETAC 1993):

1. Resource depletion 2. Land use 3. Global warming 4. Ozone depletion 5. Photochemical ozone creation 6. Acidification 7. Eutrophication, nutrification 8. Toxicological effects 9. Ecotoxicological effects 10. Waste 11. Modification of ecosystems and landscapes Prerequisites for comparative product balances

- same scope of use - same state-of-the-art technology - same range of functions

Balance factors The comparison is conducted by means of the following balance factors:

1. Extraction of raw materials, e.g. soil, sand, gravel, limestone, marl, clay, iron ore, crude oil, etc.

2. Transport of the raw materials to the site or the manufacturer 3. Production of the primary products, e.g. cement, lime, structural steel, PP granulate, etc. 4. Transport of the primary products to the manufacturer or the construction site 5. Manufacturing of the products, e.g. concrete, geogrid, geotextiles, etc. 6. Transport of the products to the construction site 7. Integration of the products, e.g. distribution, milling, consolidation, placement, etc.

Balance dimensions The cumulated energy demand (CED) is stated with the units:

- MJ/kg in relation to the product, or - MJ/m³ in relation to the compacted / stabilised soil, or - MJ/m² in relation to the compacted surface.

As a representative for the environmental impact, the CO2 emissions are indicated in kg per kg of the applied product or in kg per m³ of stabilised soil or in kg per m² of sealed area with regard to the global warming potential.

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CED (cumulated energy demand) in life cycle assessments

The multitude of environmental impacts leads to a complexity in the data collection pro-cess and to complex methods for evaluation.

If a large part of the environmental effects results from the provision and consumption of

energy, the CED may be used as a first rough check “Short life cycle assessment” in many cas-es. It provides at least first clues with regard to an ecological evaluation.

The CED is a first indicator for a rough first evaluation of the energy, transport and ma-

terial services. Even though the CED also requires data; the energy data may be collected and standardised easily (UBA 1999).

EXTRACTION AND MANUFACTURING OF THE BUILDING MATERIALS

Geosynthetics – polypropylene

Geogrid

For polypropylene, the basic material of the used geogrids, and non-woven or woven tex-tiles of the geosynthetics considered here, there are standardised data with regard to the cumulat-ed energy demand, comprising all processes from exploration, treatment and transport of the crude oil to the refinery, the distillation and steam cracking for the production of polypropylene, to the polymerisation into PP granulate and the injection moulding into a PP injection moulded part (FFE 1999):

Table 1- CED and pollution gas emissions for the production of a 1 kg PP injection moulded part

According to that, a cumulated energy demand of 78.7 MJ is necessary for one kg of ge-

ogrid and thus an amount of 2.28 kg of CO2 is emitted. The mass per unit area of the product Secugrid which is considered here amounts to 200 g/m2

(30/30 Q1) up to 620 g/m2 (60/60 Q6). The cumulated energy demand also includes the energy content (calorific value) of PP, which is approx. 47 MJ/kg.

Soil

The cumulated energy demand for buildings with soil as a construction material is com-posed of the energy demands for the excavation, transport and installation. Unlike geosynthetics, soil does not have an energy content (feedstock). Correspondingly, the CO2 emission is directly linked to the diesel consumption of the construction equipment and lorries. Special cases like oil sands or high organic soils are not considered here. Buildings made of soil generally possess

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large masses, the excavation (excavator), transport (lorry) and installation (generally fitted in with bulldozer and compacted layer by layer with a dynamic compaction roller) of which is a very energy-consuming process. The transport distance of these soil masses is in general decisive for the direct ecological comparison.

Hydraulic binding agents Fine ground lime

According to FFE (1999), a cumulated energy demand of 4663 MJ/t is necessary for the production of one ton of fine ground lime or burnt lime (CaO) and 1057 kg CO2 is emitted. Ap-proximately 75% of this is produced due to the emission of CO2 during the burning of limestone:

(CaCO3) + energy (> 900 – 1200 °C) => lime (CaO) + carbon dioxide (CO2).

Fine ground lime is used for the improvement and/or stabilisation of soils with an insuffi-cient load bearing capacity. The effect is based on the bonding of water during the transfor-mation of calcium oxide (CaO) into calcium hydroxide (Ca(OH2)), in which further water is evaporated due to the heat of reaction. As a general rule, the following applies: with 1 % by mass lime added, the optimum water content is reduced by 2%. Pursuant to FGSV - Forschungsgesell-schaft für Straßen- und Verkehrswesen, (Road and Transportation Research Association), Merk-blatt 551 (Recommendation 551), a code of practice about ground stabilisation and soil im-provement with binding agents, experimental values for binding agent quantities for the qualified improvement of soil of “3 – 4 % by mass of fine ground lime or 3 – 5 % of lime hydrate for mixed-grain and fine grain soils according to DIN EN 459-1” (original text in German) are indi-cated.

Cement

Cements are used both as binding agents for concrete and as impervious barrier masses as well as for the improvement and stabilisation of soils pursuant to ZTVV-StB 81 (Zusätzliche technische Vorschriften und Richtlinien für die Ausführung von Bodenverfestigungen und Bo-denverbesserungen im Straßenbau; Additional technical regulations and guidelines for the com-pletion of soil stabilisation and soil improvement in road construction) or FGSV 551 (2004), respectively (cements pursuant to DIN EN 197-1 or DIN 1164-10, correspondingly).

In order to produce one ton of cement clinker, 1.59 t of raw material, which consists of 76 – 78% of limestone (CaCO3), are necessary. During the burning process of the cement clinker taking place at high flame or gas temperatures of approx. 2000°C and high material temperatures (approx. 1450 °C) in a rotary tubular kiln, approx. 1/3 of the CO2 emissions derive from the burning process and approx. 2/3 are process related deriving from the decarbonisation of the limestone. In order to produce one ton of cement clinker, an energy of approx. 4056 MJ or 1127 kWh is necessary and approx. 1 t of CO2 is emitted. With a 75% content of cement clinker on average, it is the main constituent of cement. For the aforementioned reasons the cement industry attempts to replace the high cement clinker rate of e.g. Portland cement (approx. 95%) partially by other hydraulic acting aggregates e.g. blast furnace slag or scoria for so called Portland blast furnace cement, in order to reduce thus the energy and CO2 balance. Thanks to the extensive sub-

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stitution of Portland cement clinker by blast furnace slag or scoria, blast furnace cement has a considerably lower CED and CO2 emission (1669 MJ/t and 232 kg CO2/t) than Portland cement (FFE 1999). Blast furnace cement also has a lower initial strength compared to Portland cement.

In the example of the new construction of the District Road K34 in point 5.1, a Portland cement with a CED of 4290 MJ/kg and a CO2 emission of 890 kg/t as well as a subbase binder with a CED of 3500 MJ/t and a CO2 emission of 800 kg/t were used. (FFE 1999).

LOADING, TRANSPORT, INTEGRATION

Transport processes for construction materials naturally also play an important role when it comes to the ecological comparison of the construction materials and systems. Per transport ton kilometre (tkm) with a lorry an energy consumption between approx. 1.2 and 3.4 MJ/tkm can be estimated, depending on the size of the lorry (e.g. Euro trailer) and the ratio between short and long-haul traffic. A CO2 emission of 120 to 350 g/tkm is directly linked to this. Based on the production site for Secugrid considered here in Adorf, the transport distance to the construction site is statistically and naturally (almost) always larger, than that to the regionally more wide-spread lime, cement or concrete factories or extracting plants for soils. In relation to the entire Federal Republic of Germany, the products of the company NAUE have, statistically speaking, an average one-way transport distance in the range of approx. 350 km, which compared to the transport distances of the previously mentioned binding agent producers for lime and cement, is approx. 5 to 10 times longer. On average and in relation to the Federal Republic of Germany, the concrete and soil supply will be located even closer to the site than that of lime or cement. How-ever, it is at times surprising how far soil and concrete are sometimes transported solely on the basis of price differences and distortion of competition. The transport distances for geosynthetics which are on average considerably higher are generally more than counterbalanced by the con-siderably lower tonnages required for geosynthetics. As a reminder the above-mentioned com-parison is referred to again: 0.67 kg of Secugrid compared to 70 kg of fine ground lime per cubic metre of soil. Accordingly, the loading and installation of geogrids and the laying of non-woven geotextiles requires only light tracked devices (fork-lift truck, wheeled loader) or may be con-ducted on site with a excavator-wheeled loader-unit and comparatively light equipment com-pared to earthworks or special civil engineering works. For detailed data with regard to the ap-proaches considering transport distance, excavation of soil and installation of the materials please refer to Table 2. COMPARISON OF THE CONSTRUCTION METHODS BY MEANS OF AN EXAM-PLES Use of hydraulic binding agents for soil stabilisation in comparison to the use of geogrids using the example of the new construction of the district road K34 (bypass road between the K30 and the B264 Würselen), district of Aachen, 2008; see Figures 1 and 2, respective-ly.

For the new construction of the district road, a considerable advantage of the geogrid so-lution in comparison to the use of lime, cement and concrete became apparent in the form of a considerably lower CED and CO2 emission. One of the main reasons is the very small amount of geosynthetics made of polypropylene (PP) that was required, besides the high specific CED per

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kilogram of PP. On the basis of a mass per unit area of the geogrids of 200 g/m² PP and a spac-ing distance of the geogrid of 30 cm only, 0.67 kg of PP per cubic metre of soil were required for the equivalent of one cubic metre of stabilised soil.

Figure 1 - Example of base soil improvement by milling of binder (lime/cement) into the soil.

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Figure 2 - Example for base soil reinforcement with a biaxial polypropylene geogrid. Table 2 - New construction of the District Road K34 (bypass road between the K30 and the

B264 Würselen), district Aix-la-Chapelle, Germany, 2008 Announced: Soil improvement with white lime DIN EN 459-1 area [m²] mass [Mg]Soil improvement with white lime, layer thickness 40 - 45 cm, ca. 15 kg/m² 40000 600Soil improvement with white lime, layer thickness 40 - 45 cm with 3 - 4 MA.% 40000 1190Soil density [kg/m³] 2000Added amount of fine ground lime [Ma.%] 1.65 Announcement district of Aachen, 15 kg/m² fine ground lime on 40-45 cm soilAdded amount of fine ground lime [Ma.%] 3.5 Average value from FGSV bulletin soil stabilisation and improvementAdded amount of hydrated lime [Ma.%] 4 Average value from FGSV bulletin soil stabilisation and improvementAdded amount of cement [Ma.%] 4.5 Average value from FGSV bulletin soil stabilisation and improvementAdded amount of base course binder [Ma.%] 4.5 Average value from FGSV bulletin soil stabilisation and improvementDistance between geogrid layers: 0,3 m = [m²/m³] 3.33

Production PP-geogrid [MJ/kg] 78.7

Production fine ground lime [MJ/kg] 4.663 FfE (German research center for energy business, 1999)Production hydrated lime [MJ/kg] 3.553 FfE (German research center for energy business, 1999)Production cement [MJ/kg] 4.290 FfE (German research center for energy business, 1999)Production base course binder [MJ/kg] 3.500 FfE (German research center for energy business, 1999)Setting tank truck [MJ/kg] 0.002Setting geogrids with fork lift [MJ/kg] 0.090Distance to construction site lime [km] 120 Wülfrath/Flandersbach - WürselenDistance to construction site cement [km] 200 Erwitte - WürselenDistance to construction site geogrids [km] 600 Adorf - Würselenenergy consumption Eurotrailer long-distance traffic [MJ/tkm] 1.75 Capacity utilisation: 50 %; 12 t basic weight + 5 t charge (Lünser 1997)energy consumption silo truck long-distance traffic [MJ/tkm] 1.17 Capacity utilisation: 50 %; 12 t basic weight + 26 t charge (FfE 1999)Removal silo truck [MJ/kg] 0.005Removal with lightweight wheel loader [MJ/kg] 0.072Installation of geogrids with excavator or wheel loader [MJ/m²] 0.569Distribution lime/cement with distribution machine [MJ/m³] 0.541Lime/cement milling into soil [MJ/m³] 23.73Mixed in plant [MJ/m³] (optional) 6.5Soil insertion with bulldozer [MJ/m³] 8.981Soil compaction with roller compactor [MJ/m³] 5.450

Data of FfE (German research center for energy business, 1999) for extrusion of PP injection moulding parts

In order to allow for a comparative assessment, an average value pursuant to the code of

practice FGSV-Merkblatt 551 (2004) of 3.5 % by mass was considered for the addition of fine ground lime and of 4% by mass for the addition of lime hydrate. This corresponds to a 70-80 kg of fine ground lime or lime hydrate per m³ of soil at a moisture density of approx. 2000 kg/m³. The production of the much larger amount of fine ground lime required has obviously negative effects on the cumulated energy demand and the CO2 emission (cf. Tables 3 and 4).

A similar result appears for the use of cement or subbase binders for the soil stabilisation. Pursuant to the code of practice FGSV-Merkblatt 551 (2004) on average 4.5 % by mass of ce-ment or subbase binder have to be milled into the ground, which corresponds to approx. 90 kg per cubic metre of soil (for CED and CO2 emission values, see Tables 3 and 4 and Figures 3 and 4 for a graphic comparison).

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Table 3 - Cumulated energy demand for the new construction of the District Road K34

CED Cumulated energy demand [MJ/m³] fine ground

limefine ground

limehydrated

limecement base layer

binder geogrid (PP)

Product characteristics / procedure Announ. K34 FGSV FGSV FGSV FGSV 20/20 Q1 30/30 Q1 40/40 Q1 Mass per unit area [kg/m²], amount of lime etc. on 30 cm 9.88 21.00 24.00 27.00 27.00 0.16 0.20 0.24Raw material [MJ/kg] / hydration energy 1.18 1.18 0.00 0.45 0.45 43.50 43.50 43.50Production [MJ/kg] (from literary sources and manufacturer inf.) 4.66 4.66 3.55 4.29 3.50 78.70 78.70 78.70Amount required [kg/m³] 32.94 70.00 80.00 90.00 90.00 0.52 0.67 0.80Energy demand production [MJ/m³] 153.61 326.41 284.24 386.10 315.00 40.62 52.41 62.90Setting of tank truck [MJ/m³] 0.081 0.172 0.197 0.222 0.222Setting fork lift [MJ/m³] 0.05 0.06 0.07Transport to construction site [MJ/m³] 4.63 9.83 11.23 21.06 21.06 0.54 0.70 0.84Removal silo truck [MJ/m³] 0.162 0.345 0.394 0.443 0.443Removal lightweight wheel loader [MJ/m³] 0.04 0.05 0.06Soil application on demand [MJ/m³] 8.98 8.98 8.98 8.98 8.98 8.98 8.98 8.98

Binder distribution with distribution machine [MJ/m³] 0.54 0.54 0.54 0.54 0.54Milling binder lime/cement [MJ/m³] 23.73 23.73 23.73 23.73 23.73Installation => laying of geogrids [MJ/m³] 1.89 1.89 1.89Soil compaction [MJ/m³] 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45Energy consumption [MJ/m³] 197.18 375.46 334.77 446.53 375.43 57.57 69.55 80.19Cumulated energy demand (CED) for K34 [GJ] 3352 6383 5691 7591 6382 979 1182 1363

Table 4 - Cumulated CO2- emissions for the new construction of the District Road K34 Cumulated CO2 emissions [kg/m³ soil] fine ground

limefine ground

limehydrated

limecement base layer

bindergeogrid (PP)

Product characteristics / procedure Announ. K34 FGSV FGSV FGSV FGSV 20/20 Q1 30/30 Q1 40/40 Q1

Mass per unit area [kg/m2] or lime quantity etc. on 30 cm 9.88 21 24 27.00 27 0.16 0.2 0.24Production [kg CO2 per kg] 1.057 1.057 0.507 0.89 0.8 2.28 2.28 2.28Amount of hydraulic binding agent / geogrid [kg/m3] 32.94 70 80 90 90 0.52 0.67 0.8Production [kg CO2/m3 soil] 34.82 73.99 40.56 80.1 72 1.18 1.52 1.82

Loading Silo-truck transport [kg CO2/m3 soil] 0.007 0.014 0.016 0.018 0.018

Loading Fork lift truck [kg CO2/m3 soil] 0.004 0.005 0.006

Transport to site [kg CO2/m3 soil] 0.375 0.796 0.91 1.706 1.706 0.044 0.057 0.068

Unloading Silo-truck transport [kg CO2/m3 soil] 0.013 0.028 0.032 0.036 0.036

Unloading Light wheeled loader [kg CO2/m3 soil] 0 0.004 0.05

True to profile distribution of the soil [kg CO2/m3 soil] 0.728 0.728 0.728 0.728 0.728 0.728 0.728 0.728

Distributing binding agent Scatter truck [kg CO2/m3 soil] 0.044 0.044 0.044 0.044 0.044

Milling in Binding agent Lime / cement [kg CO2/m3 soil] 1.923 1.923 1.923 1.923 1.923

Installation => laying geogrids [kg CO2/m3 soil] 0.153 0.153 0.153

Compaction of soil [kg CO2/m3 soil] 0.442 0.442 0.442 0.442 0.442 0.442 0.442 0.442

Total emissions [kg CO2/m³ soil) 38.35 77.96 44.65 85 76.9 2.55 2.91 3.26

Emissions [Mg CO2] for the soil stabilisation of K34 652 1325 759 1445 1307 43 49 55

‐37‐ 

Figure 3 - Cumulated energy demand (CED) for the new construction of the District Road K34.

Production

Setting

Transport to construction site

Removal

Soil distribution

Binder distribution (distribution machine)Milling binder (rotovator)

Laying geogrids

Soil compaction

Fine ground lime1.325 t 49 t

Secugrid

6383 GJ 1182 GJFine ground lime Secugrid

‐38‐ 

Figure 4 - Cumulated CO2- emissions (tons) for the new construction of the District Road K34. SUMMARY

Polypropylene, cement, fine ground lime are high-quality materials with a very high to high CED (Cumulated Energy Demand) and a high emission of CO2 and other pollution gases. Therefore, they should only be used in an intelligent and economical manner as far as possible. Cement and lime emit up to 75% of their CO2 due to decarbonisation of the limestone or cement clinker, besides the CO2 from the energy demand for the burning of lime and cement at tempera-tures 900 to 1500 °C. Conversely, polypropylene for the use in geosynthetics has the highest cumulated energy demand and the highest CO2 emission of the materials and products consid-ered here, but it is generally only used in very small specific amounts (approx. 0.2 – 0.7 kg/m²). Compared to this, lime and cement for soil stabilisation in the example above, are used in quanti-ties of approx. 70 to 130 kg/m3. Due to the lower specific weights, loading, transport and instal-lation processes are consequently of lesser importance for geosynthetics than for soil, lime and cement. Geosynthetics have a high energy content which is included in the cumulated energy demand (CED) (polypropylene and polyethylene approx. 47 MJ/kg) in the form of the calorific value (feedstock). For this type of direct comparison with materials and products without feedstock (soil, concrete, steel) or with a negligibly low feedstock (hydration heat of lime and cement) this is an essential (but according to general opinion unchangeable) disadvantage. Nevertheless, soil stabilisation and reinforced earth constructions with geosysnthetics have a considerable advantage compared to the use of hydraulic binding agents, especially from an eco-logical point of view, thanks to the low specific weight and mass advantage. Consequently, the intelligent use of geosynthetics in geotechnics and in civil engineering not only offers cost advantages but generally also ecological advantages for the environment. How-ever, this statement cannot be generalized and has to be considered individually for each applica-tion.

REFERENCES AND RELATED LITERATURE Bundesverband der Deutschen Kalkindustrie e.V. (2006): Kalk Kompendium. Cologne. www.kalk.de.

DIN EN ISO 14044 (2006) Umweltmanagement - Ökobilanz - Anforderungen und Anleitungen (ISO 14044:2006); German and English version EN ISO 14044:2006. Beuth Verlag Berlin.

DIN EN ISO 14044 (2006) Umweltmanagement - Ökobilanz - Grundsätze und Rahmenbed-ingungen (ISO 14040:2006); German and English version EN ISO 14040:2006 Beuth Verlag Berlin.

DIN-Fachbericht 107 (2000): Umweltmanagement – Ökobilanz – Anwendungsbeispiele zu ISO 14041 zur Festlegung des Ziels und des Untersuchungsrahmens sowie zur Sachbilanz; German and English version ISO/TR 14049:2000. Beuth Verlag. Berlin.

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Egloffstein. Th.. Burkhardt. G. (2005): „Ökobilanzen für Oberflächenabdichtungssysteme – Ein Blickwinkel zur ganzheitlichen Betrachtung von Abdichtungen und Funktionsschichten“. In: Egloffstein / Burkhardt / Czurda (eds.) Abschluss und Rekultivierung von Deponien und Altlas-ten 2005. Abfallwirtschaft in Forschung und Praxis Bd. 135. Erich Schmidt Verlag. Berlin.

FFE Forschungsstelle für Energiewirtschaft der Gesellschaft für praktische Energiekunde e.V. (1999): Ganzheitliche Bilanzierung von Grundstoffen und Halbzeugen. Teil I Allgemeiner Teil. Teil II Baustoffe. Teil III Metalle. Teil IV Kunststoffe. Munich.

FGSV 551 Forschungsgesellschaft für das Straßen- und Verkehrswesen (2004): Merkblatt für Bodenverfestigungen und Bodenverbesserungen mit Bindemitteln. FGSV Verlag. Cologne.

Grießhammer. R. (1996): Entwicklungsziele für nachhaltige Produkte. In: Eberle. U.. Grießhammer. R. (ed.) Ökobilanzen und Produktlinienanalysen. Ökoinstitut Verlag. Freiburg.

Ökoinstitut (1999): Der Kumuliert Energieaufwand (KEA) im Baubereich. Darm-stadt/Karlsruhe/Weimar. Source UBA: http:\\www.oeko.de/service/kea/dateien/kea-bau.pdf

SETAC (1993): Guideline for Life Cycle Assessment – A „Code of Practice“. Society for Envi-ronmental Toxicology and Chemistry, SETAC Workshop held at Sesimbra, Portugal, 31 March – 3 April 1993, Edition 1, Brussels and Pensacola (Florida). SETAC (1993) Society for Envi-ronmental Toxicology and Chemistry: “Code of Practice”.

Umweltbundesamt (1999): KEA: mehr als eine Zahl. Basisdaten und Methoden zum Kumu-lierten Energieaufwand (KEA). Dessau.

Umweltbundesamt (2008): Climate Change 06/08. Nationaler Inventarbericht zum Deutschen Treibhausgasinventar 1990 – 2006. Berichterstattung unter der Klimarahmenkonvention der Vereinten Nationen 2008. ISSN 1862-4359. Dessau.

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A COMPARISON OF SUSTAINABILITY FOR THREE LEVEE ARMORING ALTERNATIVES Richard A. Goodrum Colbond, Inc., Enka, NC, USA ABSTRACT

Monday August 29, 2005 Hurricane Katrina slammed into the Gulf Coast in southeast Louisiana near New Orleans resulting in the most costly natural disaster in US History, and one of the deadliest. The ensuing storm surge from the Category 3 storm caused severe destruction along the Gulf Coast. Devastating property damage occurred along the coast and beaches from Florida to Texas, but the most severe loss of life was in New Orleans which flooded when the levee protection system failed catastrophically. As a result of the levee system failure it is estimated that eventually some 80% of the city and large portions of neighboring parishes were inundated with floodwaters.[1]

Investigations and hearings in the aftermath of Katrina led the US Congress to direct the

US Army Corps of Engineers to conduct a comprehensive hurricane risk reduction analysis and design, develop a full range of risk reduction measures, and consider risk reduction for storm surges equivalent to Category 5 hurricanes. To this end, in numerous studies, consideration has been given to the design (or re-design) of the surge protection floodwalls and levees which are the primary components of the hurricane protection system (HPS). [2,3] Of particular interest from the geosynthetic perspective is a recent (ongoing) study for the Department of Homeland Security by Amini and Li[4] reviewing three armoring methods for the levee system.

These three levee armoring methods consists of roller compacted concrete (RCC),

articulated concrete block (ACB) and high performance turf reinforcement mat (HPTRM). A comparison is made as to the sustainability of each system by computing the carbon footprint of each system.

BACKGROUND Most of the 350 miles of levees surrounding New Orleans actually weathered the Category 3 storm well and intact. However there was an estimated 50 points of failure reported that did occur either during or shortly after the storm made landfall. Although to this day, the failure mechanisms remain somewhat controversial, the failures were basically attributed to breaches caused by overtopping. This overtopping was further defined as resulting from the waves of rising floodwaters, the actual storm surge itself, or a combination thereof. Once the levees were overtopped, significant scour and erosion occurred on the protected side which ultimately caused the breaches. Many armoring methods have traditionally been employed in the design and construction of levees to prevent such scour and erosion. These methods include hard armor such as concrete

‐41‐  

splash pads, rip rap (placed loosely but sometimes locked in place by cement slurry), gabions, reno mattresses, articulated concrete block systems as well as soft armor alternatives in the form of geosynthetics known as turf reinforcement mats. As the engineers and authorities considered the modes of failure and most cost effective means to rebuild and restore the levee system, it became clear that armoring the landside slopes of the HPS is vital to withstanding future hurricanes and the associated storm surges. In August of 2007 the US Army Corps of Engineers conducted a “Levee Armoring Workshop” wherein certain design criteria were presented for the HPS levees. These criteria are noted in Tables 1 and 2 below. [5]

Table 1 - Levee Design Criteria for New Orleans Hurricane Protection System

Type of Levee Hurricane Protection Levee Type of Environment Coastal/Riverine Storm Surge 30 ft Design Shear 15 lb/ft2 Design Velocity 20 ft/sec Levee Design Slope 1H on 3V Levee Height 15 – 25 ft Levee Width 200 ft Levee Soil Clay Storm Duration 2 – 6 hours Soil Loss (Allowable) 1 inch

Table 2 - Additional Conditions for Levee Design

Armoring Life ≥ 50 years, UV & Corrosion Resistant Material Vegetation Cover Bermuda, Rye, Pensacola Bahia Grasses Environment Levee slopes routinely submerged in fresh and salt water Maintenance Levee boards mow grass approximately every two months

Construction Levees to be constructed in lifts – Remove/reuse armoring to place next lift?

These criteria were established by the US Army Corps of Engineers and their consultants from data gathered from the Katrina to improve the system to withstand at least a 100 year storm. LEVEE ARMORING CHOICES

The top three systems considered for levee armoring to meet these criteria were roller compacted concrete (RCC), articulated concrete block (ACB), and high performance turf reinforcement mat (HPTRM).

‐42‐  

RCC has been on the rise since the 1980’s and is frequently used in new or replacement earth and rockfill dams for water supply and flood control. The RCC recipe is similar to conventional concrete only much drier, with essentially no slump. RCC is well suited for armoring applications in that in can be placed quickly with standard earth moving equipment by utilizing dozers or modified paving machines to spread and vibratory rollers to compact similar to asphalt paving. High speed construction combined with the strength and durability of conventional concrete provide engineering economy with the desired performance. ACB is considered a hard armor, yet flexible material. The typically open cell structure of ACB’s can afford space for vegetal planting to give a natural appearance while providing solid, “hard armor” erosion control. ACB’s can be installed above or below the water line and are either hand placed non-cabled systems or placed by heavy equipment in a cabled (or mattress) system. ACB’s provide durability and versatility as well as good engineering economy in the case of levee armoring. HPTRM is a geosynthetic material and categorized as a rolled erosion control product (RECP). HPTRM is a polymer-based mat that consists of woven or extruded filaments formed into a stable network or fiber matrix. As described in Federal Highway Specification FP-03[?], HPTRM is typically used where field conditions with high loading and high survivability warrant, and generally exhibit high tensile strength relative to standard RECP’s. HPTRM is considered “soft armor” and when installed properly and fully vegetated provides exemplary reinforcement to vegetal cover. As tested in the DHS program per Amini and Li, each of the above described materials meet or exceed the design criteria set forth in Tables 1 and 2. SUSTAINABILITY DISCUSSION In recent years the concept of “sustainability” has become a continuous topic of discussion in the public dialogue. At best the definition of sustainability is somewhat of a moving target, but the concept is made manifest in both the public and private sectors in either economic or social policy or in bottom-line profitability and corporate stewardship, respectively. For the sake of this discussion the author will use the concept of stewardship to develop the comparison between materials and represent any potential conclusions. SUSTAINABILITY COMPARISON Making material comparisons of obviously differentiated engineering materials, from a technical perspective, we undoubtedly stumble into the age old “apples to oranges comparison” adage. While it seems plausible that one could compare an RCC installation with that of an ACB installation since there is some similarity – cement, aggregate and water; there is some cause for consternation when you consider the differences between a traditional material like concrete and the less traditional geosynthetic. For those who wish to wrestle with the materials evaluation the author commends the report by Amini and Li. For the sake of keeping with the GRI-24 Conference theme the author works under the assumption that the various material complies with the criteria set forth in Tables 1 and 2.

‐43‐  

Therefore, assuming the performance questions are answered, from the sustainability perspective it becomes a question of environmental and economic impact. For simplicity we basically want to take into account the carbon footprint and cost associated with the three material alternatives. Carbon footprint calculation methods are as varied as the definition of sustainability, but for the sake of fair comparison we utilize here data gathered and published by the US EPA (2005) and University of Bath (2008). [6]

The data presented in Table 3 represent the embodied energy and carbon values associated with the various material resource components that make up each of the three alternative choices of levee armoring systems. This renders a “cradle to gate” compilation of all the energy (carbon) used to get the product to the shipping dock at the factory. To complete the comparison and develop a “cradle to grave” summation for each system an additional factor must be included for delivery to the project. (Note: The energy used on site for installation is negated for this comparison.) Assumptions relative to each armoring system alternative have to be made and are also compiled in Tables 4.

Table 3 – Embodied Energy and Carbon Values for Alternative Armoring Schemes; After US EPA (2005) and University of Bath (2008). [6]

Material Carbon Values (ton CO2/ton material)

Concrete [RCC] (1:1:2; cement:sand:agg)

0.209 ton CO2/ton

Steel Fibers [RCC] 0.430 ton CO2/ton General Concrete [ACB] 0.130 ton CO2/ton Steel Cable [ACB] 2.83 ton CO2/ton Polypropylene (Geotextile) 2.70 ton CO2/ton Nylon (PA6) [HPTRM] 5.50 ton CO2/ton Top Soil [ACB & HPTRM] 0.090 ton CO2/ton Seeding [ACB & HPTM] 0.190 ton CO2/ton Diesel Fuel [All] 10.0 ton CO2/gal

‐44‐  

Table 4 – Assumptions Relative to Alternative Armoring Schemes

Armoring Material Assumptions Roller Compacted Concrete [RCC] Placed directly on prepared subgrade Eight inch thick concrete 1:1:2 concrete mix design Steel fibers at 5% by weight Weight calculated at 150 lb/ft3

Articulated Concrete Block [ACB] Mat Placed on 6 oz/yd2 geotextile on prepared subgrade Blocks are six inch thick concrete General concrete mix design ½ inch steel cable through block at 5% by weight Anchorage not included

Topsoil infill at 50 lb/yd2 Seeding at 3 lb/yd2

Weight calculated at 140 lb/ft3

High Performance Turf Reinforcement Mat [HPTRM]

Placed directly on prepared subgrade

Nylon TRM at 12 oz/yd2 (0.75 lb/yd2) Anchorage not included Topsoil infill at 50 lb/yd2 Seeding at 3 lb/yd2

The levee armoring systems are typically measured on a square yard of levee face basis, so material calculations based on one square yard of surface area, utilizing the carbon data from Table 3, are performed and noted in Appendix A. The calculations associated with the energy required to deliver the materials to the project site are performed and noted in Appendix B. Figure 1 shows the cumulative CO2 used to produce each of the three systems and affords a side-by-side comparison of the carbon footprint of each. Table 5 summarizes the data for this exercise.

Table 5 – Summary of “Tons of CO2 Emitted per Square Yard”

Armoring Alternative Materials Only Delivery Only Total CO2 RCC 0.104 ton CO2/yd2 0.449 ton CO2/yd2 0.553 ton CO2/yd2 ACB 0.0887 ton CO2/yd2 0.505 ton CO2/yd2 0.594 ton CO2/yd2 HPTRM 0.0046 ton CO2/yd2 0.082 ton CO2/yd2 0.087 ton CO2/yd2

 

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‐45‐ 

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‐46‐  

SUSTAINABILITY CONCLUSION Table 5 and Figure 1 profoundly illustrate the environmental impact from the sustainability perspective. The RCC system alternative has the highest CO2 values from a purely materials standpoint while the ACB system alternative leads from a delivery (diesel fuel) perspective. The HPTRM system alternative demonstrates a much smaller carbon footprint compared to the other two from both a materials and delivery perspective. The total impact for the HPTRM from sustainability standpoint is considerably smaller from an overall total carbon footprint – by a factor of more than six.

To drive home the stewardship concept, the HPTRM system also indicates a substantial savings from an overall project cost based on the $/SY of installed cost as noted in Table 6. One may also assume this difference could be even more dramatic if an analysis of the carbon footprint associated with system installation were also undertaken; considering that the HPTRM requires very little, if any, mechanized equipment compared to that required to place the RCC or ACB.

Additionally, the environmental impact of utilizing the “soft armor” alternative of the HPTRM has a tremendous “green” factor when compared to the “hard armor” alternatives. A fully vegetated HPTRM on the face of the levee is considerably more eco-friendly than the hard armor alternatives by providing localized cooling and a more accommodating habitat for wildlife. The ACB may be less onerous than the RCC in this regard assuming even partial vegetation establishment, which is common in these applications. But the obvious thermal impact of the paved concrete surface is notorious for contributing to localized warming, degrading the otherwise healthy wildlife habitat. And while the main purpose of the levee is structural, to prevent flooding and protect against loss, positive environmental impact and system sustainability is certainly a measure of stewardship that should weigh heavily in any engineering calculation. ACKNOWLEDGEMENTS The author would like to acknowledge Dr. Robert M. Koerner for his assistance and input in determining the carbon footprint and calculations for the material comparison. Also, Dr. Farshad Amini and Dr. Lin Li for the opportunity to utilize their research as a launch pad for this paper. REFRENCES

1. Knabb, Richard D; Rhome, Jamie R.; Brown, Daniel P (December 20, 2005; updated August 10, 2006). "Tropical Cyclone Report: Hurricane Katrina: 23–30 August 2005" (PDF). National Hurricane Center. http://www.nhc.noaa.gov/pdf/TCR-AL122005_Katrina.pdf.  

2. Andersen, Christine F. et al. (2007). "The New Orleans Hurricane Protection System: What Went Wrong and Why" (PDF). American Society of Civil Engineers Hurricane Katrina External Review Panel.

3. Seed, R.B.; et al. "Preliminary Report on the Performance of the New Orleans Levee Systems in Hurricane Katrina on August 29, 2005." University of California, Berkeley. November 2, 2005 

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4. Amini, F. and Li, L., (2011). [Work-in-progress (not yet published) investigating the performance of Three Alternatives for Armoring Levees, Jackson State University report for Department of Homeland Security.

5. Villa, April, (2007). Levee Armoring Workshop, sponsored by US Army Corps of Engineers, New Orleans District, New Orleans, LA., 2007.

6. Hammond, G. and Jones, C., Inventory of Carbon and Energy (ICE), version 1.6a, University of Bath, UK, 2008.

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Appendix A – Materials Calculations Based on One Square Yard of Surface Area

RCC Calculations

Concrete: (8/12)(1x1)(150)(9) = 0.45 x 0.209 2000 = 0.0941 ton CO2Steel Fibers: 0.45 x 0.05 = 0.0225 x 0.430 = 0.0097 ton CO2

RCC Materials Footprint = 0.104 ton CO2/yd2

ACB Calculations

Geotextile (PP): 0.375 = 0.00019 x 2.7 2000 = 0.0005 ton CO2

Concrete: (6/12)(1x1)(140)(9) = 0.315 x 0.130 2000 = 0.0410 ton CO2 Steel Cable: 0.315 x 0.05 = 0.158 x 2.83 = 0.0446 ton CO2

Topsoil: 50 = 0.025 x 0.090 2000 = 0.0023 ton CO2

Seeding: 3 = 0.0015 x 0.190 2000 = 0.00028 ton CO2

ACB Materials Footprint = 0.08868 ton CO2/yd2

HPTRM Calculations

HPTRM (Nylon6): 0.75 = 0.000375 x 5.5 2000 = 0.0020625 ton CO2

Topsoil: 50 = 0.025 x 0.090 2000 = 0.0023 ton CO2

Seeding: 3 = 0.0015 x 0.190 2000 = 0.00028 ton CO2

HPTRM Materials Footprint = 0.0046425 ton CO2/yd2

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Appendix B – Delivery Calculations Based on One Square Yard of Surface Area

RCC Calculation

• Plant located 20 miles for site • Truck estimated mpg at 4 mi/gal • Capacity 20 yd3 per truck

4 gal x 8 = 0.0444 x 10.1 = 0.449 ton CO2/yd2 20 yd3 36

ACB Calculation

• Plant located 40 miles for site • Truck estimated mpg at 10 mi/gal • Capacity 80 yd2 ACB mat per truck

4 gal = 0.05 x 10.1 = 0.505 ton CO2/yd2 80 yd2

HPTRM Calculation

• Plant located 650 miles for site • Truck estimated mpg at 10 mi/gal • Capacity 8000 yd2 ACB mat per truck

65 gal = 0.008125 x 10.1 = 0.08206 ton CO2/yd2 8000 yd2

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SUSTAINABILITY ASPECTS OF THE FIBER REINFORCED SOIL REPAIR OF A ROADWAY EMBANKMENT Garry H. Gregory, Ph.D., P. E., D.GE Principal Consultant, Gregory Geotechnical, Stillwater, OK; Adjunct Professor of Civil Engineering – Oklahoma State University ABSTRACT

This paper addresses the Fiber-Reinforced Soil (FRS) repair of approximately 2,100 linear meters (7,000 linear ft) of shallow slope repairs along a portion of Lake Ridge Parkway adjacent to Joe Pool Lake in Grand Prairie, Texas. The project required approximately 73,000 m3 (96,000 yd3) of compacted earth fill consisting of FRS. The project utilized about 294,000 kg (648,000 lbs) of polypropylene fibers, making it one of the largest earthwork projects ever constructed with FRS fill. Lake Ridge Parkway was constructed in the early 1980s with earth fill embankments to raise the roadway grade above the reservoir level of the newly constructed Joe Pool Lake in southern Dallas and Tarrant Counties, Texas. The embankments were constructed of residual fat clays of the Eagle Ford geologic formation, which were the only locally available soils. Over the ensuing years the embankments began experiencing shallow slope failures in the range of 2 to 3 m (6 to 10 ft) in depth, which began impacting the roadway pavements by about 2002. No additional space was available for flattening the slopes due to the adjacent lake. Conventional repair of the slopes would have required excavating and removing the existing clay soils and replacing with imported select fill. The FRS option allowed reuse of the existing clay embankment soils which were excavated in short sections and replaced in lifts as fibers were added to produce the FRS fill. The FRS option not only provided a long-term cost effective solution, but also significantly enhanced sustainability by eliminating the need to expend large amounts of truck fuel hauling in select fill from long distances and hauling away clay spoil. Elimination of the need for the select fill hauling operation also reduced the heavy truck traffic on the roadway pavement, extending the remaining life of the pavement and reducing carbon emissions from the trucks. The FRS slope repairs were accomplished in two phases completed in 2004 and 2007, respectively. INTRODUCTION Site History Joe Pool Lake was constructed in southern Dallas and Tarrant Counties, Texas in the late 1970s and early 1980s under the direction of the U. S. Army Corps of Engineers. A portion of Lake Ridge Parkway, a rural arterial roadway, was located in the reservoir foot print of the proposed lake. Accordingly, it was necessary to raise the roadway above the flood level of the lake. This was accomplished by construction of earth fill embankments and two bridges at selected locations. The embankments were constructed with 3 horizontal to 1 vertical side slopes (slope ratio of 3) and ranged from about two m (6 feet) to approximately 6 m (20 feet) in vertical height above the water level. The only locally available fill material was high plasticity residual clay of the Eagle Ford geologic formation. Soil-cement erosion protection was installed along the lower portion of the slopes and extended below water level to the bottom of the adjacent lake.

The left extendedisolated years aftshallow spread anshallow f

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‐51‐ 

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‐52‐ 

FRS option was $3,750,000. The estimated cost of the select fill option was $6,234,000. A major factor in the large difference in cost between these two options was a distance of approximately 24 km (15 miles) to the near known source of suitable select fill. The initial cost estimates included the entire 2,100 linear m of slopes. The project was later separated into two phases. Phase I was completed in 2004 and Phase II was completed in 2007. Other options were considered which included FRS in combination with other reinforcing elements such as drilled shafts and soil nails. However, the full FRS option was the most cost effective of those considered and was the only option bid. The actual contractor bids were well within the estimates for both phases. Carbon Footprint Comparison Carbon footprint comparison is made between the FRS option and the Select Fill option based on embodied carbon values (U.S. EPA 2005; University of Bath 2008) of the various materials and the required fuel for hauling of the select fill. The required construction operations and quantities for each option are presented in Tables 1 and 2.

Table 1 – Required Construction Operations and Material Quantities – “FRS Option”

Activity Material Reqd. Quantity/Unit CO2 Units kg CO2 Excavate and Stockpile- Site Diesel Fuel 6,000 gal 10.1 60,600

Mix and Recompact FRS Diesel Fuel 6,000 gal 10.1 60,600 Mix and Recompact FRS Gasoline 7,000 gal 8.8 61,600 Excavate and Recompact Earth Fill 147E+6 kg 0.023 3,381,000

Provide Fibers PP Fibers 294,000 kg 2.7 793,800

Total kg CO2 Emitted 4,357,600 Total kg CO2 Emitted per m2 (based on 34,000 m2 surface area) 128

Table 2 – Required Construction Operations and Material Quantities – “Select Fill Option”

Activity Material Reqd Quantity/Unit CO2 Units kg CO2 Excavate and Load- Borrow Pit Diesel Fuel 6,000 gal 10.1 60,600 Excavate and Load- Borrow Pit Earth Fill 147E+6 kg 0.023 3,381,000

Haul Select Fill to Site Diesel Fuel 19,200 gal* 10.1 161,600 Excavate Spoil at Site Diesel Fuel 6,000 gal 10.1 60,600 Haul Spoil to Refill Pit Diesel Fuel 19,200 gal 10.1 161,600

Unload and Compact Spoil Diesel Fuel 6,000 gal 10.1 60,600 Unload and Compact Spoil Spoil Fill 147E+6 kg 0.023 3,381,000

Unload and Compact Select Fill Gasoline 7,000 gal 8.8 61,600 Unload and Compact Select Fill Earth Fill 147E+6 kg 0.023 3,381,000

( *1 gallon = 3.8 liter) Total kg CO2 Emitted 10,709,600

Total kg CO2 Emitted per m2 (based on 34,000 m2 surface area) 315

Ta bulk lotruck. Thway. TheMiller (2 CONCL Tpercent ocarbon frelativelyrecompacthis proje Tconstruct

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‐53‐ 

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‐54‐ 

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‐55‐ 

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‐56‐ 

REFERENCES Benson, C. H., and Khire, M. V. (1994), “Reinforcing Sand with Strips of Reclaimed High-Density Polyethylene,” Journal of Geotechnical Engineering, Vol. 120, No. 5, pp. 838-855.

Dewar, J. F. (2003), “City of Grand Prairie-Lake Ridge Parkway Repair at Joe Pool Lake Bridges.” Freese and Nichols, Inc.- Design Report, January 5, 2003.

Gray, D. H. and Ohashi, H. (1983), “Mechanics of Fiber Reinforcement in Sand,” J. Geotechnical Engineering, ASCE, Vol 109, No. 3, pp. 335-353.

Gregory, G. H. (1996) “Laboratory Testing of Fiber-Reinforced Soils,” Proceedings – FHWA - 29th Annual Southeastern Transportation Geotechnical Engineering Conference, Cocoa Beach, Florida, USA996. Gregory, G. H. (1997) “Slope Reinforcement Using Randomly – Distributed Polypropylene Fibers,” Proceedings - FHWA - 22nd Annual Southwest Geotechnical Engineers Conference, Santa Fe, New Mexico. Gregory, G. H. (1998a) “Long -Term Repair of Slopes with Fiber Reinforcement,” Proceedings – FHWA - 23rd Annual Southwest Geotechnical Engineers Conference, Reno, Nevada, USA. Gregory, G. H. (1998b) “Reinforced Slopes Using Geotextile-Fibers Composite,” Proceedings - FHWA-30th Annual Southeastern Transportation Geotechnical Engineering Conference, Louisville, Kentucky. Gregory, G. H. and Chill, D. S. (1998). “Stabilization of Earth Slopes with Fiber Reinforcement,” Proceedings of the Sixth International Conference on Geosynthetics, Atlanta, Georgia. Gregory, G. H. (1999a). “Theoretical Shear-Strength Model of Fiber-Soil Composite,” Proceedings-ASCE Texas Section Spring Meeting, Longview, Texas99. Gregory, G. H. (1999b). “Fiber-Reinforced Soil – A Key Role in Geosynthetics Applications for the 21st Century,” Invited Paper, Proceedings – GRI-13 Conference on Geosynthetics in the Future, GII Publ., Folsom, PA, USA, pp. 164-171. Gregory, G. H. (2006). “Shear Strength, Creep, and Stability of Fiber-Reinforced Soil Slopes.” Doctoral Dissertation submitted to the Faculty of the Graduate College of Oklahoma State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy, May 2006, 225 pp. Miller, N. (2010). Personal communication with Mr. Neil Miller of Cooper Excavation, Inc. (Earthwork Contractor for the Project).

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University of Bath (2008). “Inventory of Carbon Energy.” Version 1.6a. U.S. EPA (2005). “Emission Facts” Office of Transportation and Air Quality, EPA 420-F-05-001, Risk Reduction Laboratory, Office of Research and Development, Cincinnati, Ohio.

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REDUCTION OF CLIMATE-DAMAGING GASES IN GEOTECHNICAL ENGINEERING BY USE OF GEOSYNTHETICS

Kent von Maubeuge, Naue GmbH & Co. KG, Espelkamp, Germany Georg Heerten, Naue GmbH & Co. KG, Espelkamp, Germany Thomas A. Egloffstein, ICP Ingenieurgesellschaft mbH, Karlsruhe, Germany ABSTRACT

At present, the political discussions around the globe are focused on sustainable

development. Demand for reduction of energy consumption and emission of climate related gases like CO2 and CH4 are major challenges for the construction industry, too.

Economical and ecological advantages of construction methods with geosynthetics are

already well known. Emissions from soil masses that need to be excavated, transported and installed can be dramatically reduced. The best examples are those of geosynthetic clay liners or geocomposite drains instead of clay or gravel layers. But also the avoidance of soil exchange in traffic areas and the improvement of soil at site with geogrids have to be mentioned as positive examples in this regard. This paper will conduct a comparison between classical construction techniques and geosynthetic construction alternatives. The cumulated energy demand (CED) and climate related CO2 emission for primary, prefinished and finished products, their transport to the manufacturer and to the construction site as well as their installation are determined. For both examples a considerably smaller cumulated energy demand (CED) and CO2 emission is shown for the geosynthetic alternatives.

INTRODUCTION

The political discussion, but also research and science, are currently affected by the claim

of "sustainable development". In the original context, "sustainable development" is not only restricted to the

requirements of saving energy and raw materials, but comprises a model of a worldwide sustainable development based on the components protection of natural resources, social and economical balance worldwide as well as the future ability to develop with regard to education and economical scope of action.

The will and ability to achieve these sustainable aims will decide on our future;

completely independent of hypothetical climate change scenario with more or less anthropogenic influence and hardly predictable regional impacts. The worldwide propagated climate protection approach to save energy and to reduce radically the emissions of the global warming gases CO2 (carbon dioxide), but also CH4 (methane) with its approx. twenty times higher damage to the climate compared to CO2, are important components for a successful sustainable development and are therefore to be supported without restrictions.

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The construction industry is a key industry responsible for 10 % of the employees worldwide and 7 % of the total economic performance. Approximately 40 % of the worldwide energy consumption and greenhouse gas emission, significantly influenced by buildings (heating and cooling) which are not energy efficient to a large extent, are to be assigned to the construction industry. There is a tremendous potential for sustainable developments in the construction industry including geotechnical, hydraulic and coastal engineering.

Innovations were and are essentially influenced by cost minimising. To encourage

sustainable developments for constructions, sustainability components such as energy consumption or emission of greenhouse gases would have to be determined and calculated in offers.

For two infrastructure projects – new construction of a district road and completion of a

slope protection – Life Cycle Assessments (LCA) for alternative construction methods were made. As for these two examples from the construction industry the energy demand and associated emission of greenhouse gases demonstrate the decisive impacts on the environment, the cumulated energy demand (CED) and the CO2 emission can be used as "short LCA" for the ecological evaluation. Taking into account the extraction and production of the used construction materials, loading, transport and installation, the cumulated energy demand (CED) and CO2 emissions are determined for each of the construction alternatives.

For an environmentally friendly evaluation of the alternatives, the money equivalent of the

CO2 emissions would have to be determined and the costs for CO2 emission certificates would have to be added to the quoted price for the construction work. Only in this manner the most sustainable offer could be accepted.

It is a challenging task for present research and development activities to support

sustainable developments on the globe in favour of our future. Since many years already, it is reported about economical and ecological advantages of

construction methods with geosynthetics in geotechnics and hydraulic engineering. Comparing traditional construction methods with those using geosynthetics, the latter result in considerable reduction of construction costs and/or construction time and considerably less masses that have to be excavated, transported and installed. In addition, there are environmental advantages, for example due to the possibility of green geogrid reinforced slopes (Fig. 1) or the natural settlement of marine flora and fauna in coast protection measures, as for example shown at the artificial reef consisting of "geotextile containers" at the Gold Coast in Australia (Heerten et al, 2000).

Also the application of geogrids for base soil reinforcement in traffic areas instead of

milling lime/cement binder into the soil is showing environmental advantages by having no groundwater impact and no air pollution due to lime/cement dust.

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Figure 1 - Example of a greened up geogrid reinforced supporting structure city railway in

Stuttgart, Germany (1990).

PRESENT ECONOMICAL AND ECOLOGICAL ADVANTAGES OF GEOSYNTHETIC CONSTRUCTION METHODS

The cover sealing of the old and closed landfill Neu Wulmstorf near Hamburg was one of

the first big projects (320,000 m² / 32 ha) in Germany where a classic/traditional cover system with clay liner and gravel drainage layer was replaced by a geosynthetic alternative. The cover system – consisting of a geosynthetic clay liner (GCL), a HDPE geomembrane and a geosynthetic drainage layer - was carried out on a mineral leveling layer permeable to gas placed on top of the waste. Fig. 2 shows the project in 1996.

For this project, it could be established that

instead of 21,000 truck loads for clay and gravel only 165 truck loads were necessary for the supply of GCL and geosynthetic drainage layer,

instead of the projected construction costs of approx. 36 million Euro only costs of approx. 25 million Euro occurred and thus 30 % of the projected costs could be reduced,

instead of a construction period of approx. three years the project could be completed within two years.

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Figure 2 - Installation of a geosynthetic clay liner (GCL) as part of a geosynthetic cover system at the landfill Neu Wulmstorf near Hamburg, Germany, 1996/97.

With another project carried out in 1999, the landfill Lichte near Stuttgart, Germany, a

cost reduction of 47 % could be achieved by using alternative geosynthetic construction methods. In this case a geocomposite drain was used as landfill gas collecting layer, a GCL and geomembrane as combination sealing and a geocomposite drain again as drainage layer for seepage water out of the cover soil.

In addition to these savings and advantages, it has to be pointed out for cover systems in landfills that the landfill's climate damaging potential resulting from the possible emission of methane (CH4) can be reduced by a factor of twenty, if the methane (CH4) is being collected and used for energy production or simply burnt off. Thus, only carbon dioxide (CO2) would be emitted instead of methane (CH4).

Also for geosynthetic reinforced steep walls or slopes, construction costs of 30 to 50 % can be saved in comparison to classic construction methods (Fig. 3, Koerner et al., 1998).

Figure 3 – The money challenge (MSE = Mechanically Stabilised Earth).

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LIFE CYCLE ASSESSMENT

A Life Cycle Assessment (LCA) denotes the systematic analysis of the environmental impact of products during their entire life cycle (excavation and treatment of raw materials, production, distribution and transport, use, consumption and disposal). This comprises any environmental impact during the production, utilization phase and disposal of the product as well as the upstream and downstream processes connected to that (e.g. production of raw and process materials). Environmental impact may include any ecologically relevant extraction from the environment (e.g. raw oil, soil, ore), as well as emission into the environment (e.g. waste, carbon dioxide emissions).

Figure 4 shows the phases of a life cycle assessment and the correlation between the terms

life cycle inventory analysis, impact balance or impact assessment, respectively, and evaluation. Direct applications of life cycle assessments comprise for instance the development and improvement of products, strategic planning, political decision making processes or marketing etc.

Figure 4 - Constituents of a life cycle assessment (pursuant to DIN EN ISO 14040 2006-10 / 14044, 2006-10)

In the interest of a subsequent and possibly comprehensive evaluation it is reasonable to conduct an impact related account between the sole life cycle inventory analysis and the evaluation of the balance. The flow and inventory parameters collected in the life cycle inventory analysis are described or assessed, respectively, with regard to their potential effects. Their impact on selected global and regional or local environmental factors are considered. The effects from the life cycle inventory analysis may be analysed with regard to the following environmental categoies (SETAC, 1993):

1. Resource depletion 2. Land use 3. Global warming 4. Ozone depletion

Live cycle assessment (LCA)

Environmental balance

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5. Photochemical ozone creation 6. Acidification 7. Eutrophication, nutrification 8. Toxicological effects 9. Ecotoxicological effects 10. Waste 11. Modification of ecosystems and landscapes

To establish comparative life cycle balances for different products the following

preconditions are necessary:

same scope of use same state-of-the-art technology same range of functions

The comparison is conducted by means of the following balance factors:

1. Excavation of raw materials (e.g. soil, sand, gravel, limestone, marl, clay, iron ore, crude oil, etc.)

2. Transport of the raw materials to the site or the manufacturer 3. Production of the primary products (e.g. cement, lime, structural steel, PP granulate,

etc.) 4. Transport of the primary products to the manufacturer or the construction site 5. Manufacturing of the products (e.g. concrete, geogrid, geotextiles, etc.) 6. Transport of the products to the construction site 7. Integration of the products (e.g. distribution, milling, consolidation, placement, etc.)

Considering these factors, it is possible to calculate the cumulated energy demand (CED)

which can be stated with the following different units:

MJ/kg in relation to the product, or MJ/m³ in relation to the compacted/stabilised soil, or MJ/m² in relation to the sealed surface.

As a representative for the environmental impact, the CO2 emissions are indicated in kg

per kg of the applied product or in kg per m³ of stabilised soil or in kg per m² of sealed area with regard to the global warming potential.

If a large part of the environmental effects results from the supply and consumption of energy, the CED may be used as a first rough check "Short life cycle assessment" in many cases. It provides at least first clues with regard to an ecological evaluation.

The CED is a first indicator for a rough first evaluation of the energy, transport and material services. Even though the CED also requires data, the energy data may be collected and standardised easily. The FFE (Research Institute for Energy Economy) in Germany offers a significant amount of energy data.

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COMPARISON OF DIFFERENT CONSTRUCTION MEHTODS BASED ON TWO EXAMPLES

Different building materials

When comparing traditional construction methods with the use of geosynthetics on the

basis of CED or CO2 emission, one has to evaluate the excavation and production of all different construction materials needed. Transportation to the construction site and installation of the construction material or product has also to be considered. For one example of slope protection and one example of surface sealing of a river dyke with involvement of NAUE geosynthetic products the details have been worked out by ICP Ingenieurgesellschaft Prof. Czurda und Partner mbH (geologists and engineers for water and soil), Karlsruhe, in collaboration with NAUE, and have been published with a lot of details by Egloffstein (2009). Detailed information of the special used geogrids, geotextiles, different soils, fine ground lime, cement, geosynthetic barriers, structural steel have been collected and considered for CED and CO2 emission comparison. The quantities of different materials have been considered as put out to tender or defined by special offer / construction proposal or as they are recommended by technical guidelines. More details are given in Egloffstein 2009.

The slope protection example

In the vicinity of Frankfurt/Main, Germany, a new connecting road (Gänsbergspange Idstein) should improve the local traffic conditions. The design put out to tender was asking for a vertical gravity wall to support the road section. An alternative design with a geogrid reinforced slope was presented (Fig. 5) and finally built, giving the background to compare these alternatives with regard to their environmental impact.

Figure 5 - Road construction alternatives at Gänsbergspange Idstein, Germany.

The comparison between a slope protection system with geogrids including a vegetative

steep slope protection system with anti-erosion mat and a vertical gravity retaining wall made of reinforced concrete also showed considerably better results for the geosynthetics solution with regard to both the cumulated energy demand (CED) and the CO2 emissions.

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The geosynthetics solution requires not only 5350 m² of geogrid layers made of polypropylene, but also a 0.5 x 0.5 x 140 m long reinforced concrete top beam, forming the upper cover of the slope construction. In addition, 41 m² of faced brickwork made of natural stone and 630 m² of the slope protection system Deltagreen, with almost 7 kg of steel wire per square metre as well as a 200 g/m² non-woven made of PP had to be integrated into the slope protection system. Within the scope of an energy and CO2 balance, the system components had to be considered individually for the comparison with the vertical gravity retaining wall construction. Furthermore, the geogrid reinforced embankment construction required approx. 40 % more soil to be excavated, transported and installed compared to the vertical gravity retaining wall. The details are given in Table 1.

Table 1 - Cumulated energy demand (CED) for all components involved in the geogrid reinforced steep slope alternative (Project: Gänsbergspange near Frankfurt, Germany)

All this has proven not only considerably less energy consumed but also better ecology

with regard to CO2 emissions than the production, transport and installation of 1107 m³ of concrete with approx. 77.5 t of steel reinforcement. In this process, the steel reinforcement in the concrete contributed considerably to the higher CED and CO2 emissions as can be seen in Table 2. The cumulated energy demand CED for the geosynthetics solution only amounted to approx. 30 % and the CO2 emissions to approx. 18 % of the traditional alternative with vertical gravity retaining wall. Figure 6 presents more details showing the CED and CO2 emissions of the alternative construction solutions. The cumulated engery demand (CED) is about 3.5 times and

Geogrid-reinforced steep slope Data [unit] Mass [unit] Data [unit] CED [MJ]

Production Secugrid 60/60 Q6 built in area: 3.750 m²

Mass per unit area: 0,62 kg/m² 2.325 kg 78,70 MJ/kg 182.978

Production Secugrid 120/40 R6 built in area: 1600 m²

Mass per unit area: 0,58 kg/m² 928 kg 78,70 MJ/kg 73.034Transport to construction site, distance to manufacturer in Adorf 400 km 3,253 t 1,5 MJ/tkm 1.952Delta Green wire grating reinforcement system for outer slope 630 m²Production geotextiles per m² slope reinforcement made of PP 0,16 kg/m² 100,8 kgProduction polypropylene granules 0,16 kg/m² 65,50 MJ/kg 6.602Production polypropylene fibres 0,16 kg/m² 1,908 MJ/kg 192Production non-woven polyproyplene 0,16 kg/m² 0,324 MJ/kg 33

Production wire grating reinforcement; front/bottom grating, press-lock, d = 5 mm, l x w = 3 m x 0,7 m = 2,1 m², 14,6 kg per element 6,95 kg/m² 4.380 kg 27,69 MJ/kg 121.282

Transport non-woven to construction site, distance to manufacturer 270 km 0,1008 t 2,5 MJ/tkm 68

Transport wire grating to construction site, distance to manufacturer 220 km 4,38 t 1,5 MJ/tkm 1.445Installation by excavator wheel loader (Secugrid + Delta Green) 5.980 m² 1,04 MJ/m² 6.219Soil exploitation by backhoe 8.500 m³ 8.500 m³ 7,6 MJ/m³ 64.600

Soil transport 17.000 t, transportation distance 15 km 15 km 17.000 t 2,5 MJ/tkm 637.500

Soil insertion by bulldozer, layer thickness 0,30 m 8.500 m³ 8,98 MJ/m³ 76.330Soil compaction by roller compactor, layer thickness 0,30 m 8.500 m³ 4,80 MJ/m³ 40.796

Production anchored reinforced concrete ridgepole (0,5m x 0,5m x 140 m) 35 m³ 2,4 t/m³ 658 MJ/t 55.272

Production concrete reinforcing steel ST 500/550 77 kg/m³ 2,7 t 27.960 MJ/t 75.352

Transport concrete from concrete factory to construction site 20 km 84 t 2,5 MJ/tkm 4200Transport structural steel to construction site 50 km 2,7 t 2,5 MJ/tkm 337Production concrete ridgepoles (excavator, wheel loader, concrete pump etc.) 35 m³ 2,4 t/m³ 15 MJ/m³ 525

Faced brickwork of natural stones A = 41 m²; t = 0,2 m; density = 2,7 t/m³ 41 m² 8,2 m³

Exploitation faced brickwork of natural stones in quarry 22,14 t 40 MJ/t 886Transport faced brickwork from quarry to construction site 35 km 22,14 t 2 MJ/tkm 44Production faced brickwork (excavator, wheel loader etc.) 35 m³ 15 MJ/m³ 525

Total CED [GJ] 1350 GJ

Geogrid-reinforced steep slope Data [unit] Mass [unit] Data [unit] CED [MJ]

Production Secugrid 60/60 Q6 built in area: 3.750 m²

Mass per unit area: 0,62 kg/m² 2.325 kg 78,70 MJ/kg 182.978

Production Secugrid 120/40 R6 built in area: 1600 m²

Mass per unit area: 0,58 kg/m² 928 kg 78,70 MJ/kg 73.034Transport to construction site, distance to manufacturer in Adorf 400 km 3,253 t 1,5 MJ/tkm 1.952Delta Green wire grating reinforcement system for outer slope 630 m²Production geotextiles per m² slope reinforcement made of PP 0,16 kg/m² 100,8 kgProduction polypropylene granules 0,16 kg/m² 65,50 MJ/kg 6.602Production polypropylene fibres 0,16 kg/m² 1,908 MJ/kg 192Production non-woven polyproyplene 0,16 kg/m² 0,324 MJ/kg 33

Production wire grating reinforcement; front/bottom grating, press-lock, d = 5 mm, l x w = 3 m x 0,7 m = 2,1 m², 14,6 kg per element 6,95 kg/m² 4.380 kg 27,69 MJ/kg 121.282

Transport non-woven to construction site, distance to manufacturer 270 km 0,1008 t 2,5 MJ/tkm 68

Transport wire grating to construction site, distance to manufacturer 220 km 4,38 t 1,5 MJ/tkm 1.445Installation by excavator wheel loader (Secugrid + Delta Green) 5.980 m² 1,04 MJ/m² 6.219Soil exploitation by backhoe 8.500 m³ 8.500 m³ 7,6 MJ/m³ 64.600

Soil transport 17.000 t, transportation distance 15 km 15 km 17.000 t 2,5 MJ/tkm 637.500

Soil insertion by bulldozer, layer thickness 0,30 m 8.500 m³ 8,98 MJ/m³ 76.330Soil compaction by roller compactor, layer thickness 0,30 m 8.500 m³ 4,80 MJ/m³ 40.796

Production anchored reinforced concrete ridgepole (0,5m x 0,5m x 140 m) 35 m³ 2,4 t/m³ 658 MJ/t 55.272

Production concrete reinforcing steel ST 500/550 77 kg/m³ 2,7 t 27.960 MJ/t 75.352

Transport concrete from concrete factory to construction site 20 km 84 t 2,5 MJ/tkm 4200Transport structural steel to construction site 50 km 2,7 t 2,5 MJ/tkm 337Production concrete ridgepoles (excavator, wheel loader, concrete pump etc.) 35 m³ 2,4 t/m³ 15 MJ/m³ 525

Faced brickwork of natural stones A = 41 m²; t = 0,2 m; density = 2,7 t/m³ 41 m² 8,2 m³

Exploitation faced brickwork of natural stones in quarry 22,14 t 40 MJ/t 886Transport faced brickwork from quarry to construction site 35 km 22,14 t 2 MJ/tkm 44Production faced brickwork (excavator, wheel loader etc.) 35 m³ 15 MJ/m³ 525

Total CED [GJ] 1350 GJ

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the CO2 emission of the geosynthetic solution is about 5.4 times less than the traditional construction approach with a vertical gravity retaining wall construction.

Table 2 - Cumulated energy demand (CED) for all components of the vertical retaining wall

alternative (Project: Gänsbergspange near Frankfurt, Germany)

Figure 6 - Cumulated energy demand (CED) at Gänsbergspange near Frankfurt, Germany.

1350 GJ4552 GJ

Angular retaining wall

Secugrid +

Delta Green

Angular retaining wall Data [unit] Mass [unit] Data [unit] CED [MJ]

Total length 150 m

Average height 5,5 m

Angular retaining wall, average cross-sectional area (min. = 1,8 m²; max. = 9,5 m²) 7,38 m²

Production standard concrete C20/25 1.107 m³ 2,4 t/m³ 657 MJ/t 1.745.518

Transport concrete from concrete factory to construction site 20 km 2.657 t 2,5 MJ/tkm 132.840

Production concrete reinforcing steel ST 500/550, 70 kg/m³ for angular retaining wall 77,49 t 27.690 MJ/t 2.145.698

Transport structural steel to construction site 50 km 77,49 t 2,5 MJ/tkm 9.686

Production angular retaining wall (excavator, wheel loader, concrete pump etc.) 1.107 m³ 15 MJ/m³ 16.605

Soil exploitation by backhoe 8.500 m³ 5.146 m³ 7,6 MJ/m³ 39.110

Soil transport 10.292 t, transportation distance 15 km 15 km 10.292 t 2,5 MJ/tkm 385.950

Soil insertion by bulldozer, layer thickness 0,30 m 5.146 m³ 8,98 MJ/m³ 46.213

Soil compaction by roller compactor, layer thickness 0,30 m 5.146 m³ 5,40 MJ/m³ 27.790

Total CED [GJ] 4552 GJ

Angular retaining wall Data [unit] Mass [unit] Data [unit] CED [MJ]

Total length 150 m

Average height 5,5 m

Angular retaining wall, average cross-sectional area (min. = 1,8 m²; max. = 9,5 m²) 7,38 m²

Production standard concrete C20/25 1.107 m³ 2,4 t/m³ 657 MJ/t 1.745.518

Transport concrete from concrete factory to construction site 20 km 2.657 t 2,5 MJ/tkm 132.840

Production concrete reinforcing steel ST 500/550, 70 kg/m³ for angular retaining wall 77,49 t 27.690 MJ/t 2.145.698

Transport structural steel to construction site 50 km 77,49 t 2,5 MJ/tkm 9.686

Production angular retaining wall (excavator, wheel loader, concrete pump etc.) 1.107 m³ 15 MJ/m³ 16.605

Soil exploitation by backhoe 8.500 m³ 5.146 m³ 7,6 MJ/m³ 39.110

Soil transport 10.292 t, transportation distance 15 km 15 km 10.292 t 2,5 MJ/tkm 385.950

Soil insertion by bulldozer, layer thickness 0,30 m 5.146 m³ 8,98 MJ/m³ 46.213

Soil compaction by roller compactor, layer thickness 0,30 m 5.146 m³ 5,40 MJ/m³ 27.790

Total CED [GJ] 4552 GJ

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Figure 6 (cont.) - Cumulated CO2 emissions at Gänsbergspange near Frankfurt, Germany.

Different sealing materials

The comparison of an external sealing for a river dyke on the Kinzig (southwest Germany) using a geosynthetic clay sealing liner (GCL or GBR-C) with a mineral sealing according to the DWA Leaflet “Sealing Systems in Dykes with an average thickness of 0.625 m also turns out in favour of the geosynthetic clay sealing liner (CED = 71.8 to 122.3 MJ/m²). The difference in the cumulated energy demand of the two sealing systems is, however, comparatively insignificant. A medium transport distance of 35 km (one-way) was assumed for the mineral sealing material, which makes up a lion’s share of the CED for the required sealing material of 45.000 tons. For the bentonite mat the main share in the CED is the polypropylene, which at a surface weight of 0.69 kg/m² PP (incl. 6.2% overlapping) is a major factor. When comparing the two sealing systems, the transport distance for the mineral sealing material is the decisive parameter. If the place of extraction is on-site or very near to the place of installation, then the mineral sealing - mostly because it has no energy content (feedstock) - can hardly be improved upon. In the case of the bentonite mat, the main part of the CED is the energy content (feedstock) of the polypropylene (ca. 53%). The transport distance for the GCLs from the manufacturer’s plant in Espelkamp to Offenburg (580 km) is, in comparison as regards the CED compared to the PP granulate material, of hardly decisive consequence (ca. 8.5%).

The covering soil which has to be put in position as weather protection for both sealing methods (here: d = 0.8 m), is 97 MJ/m² with an assumed average transport distance of 20 km for both surface sealing systems, in particular when comparing these systems with other systems, of quite considerable consequence. The distribution concerning environmentally relevant CO2 corresponds approximately to the CED, the bentonite mat has a CO2 emission of 4.0 kg/m², the mineral sealing of 9.9 kg/m² and the covering soil is entered in the CO2 balance sheet with 7.9 kg/m². Tables 3, 4 aned 5 present data from which CED-values were calculated and Figures 7 and 8 show these details graphically.

542 t CO2101 t CO2

Angular

retaining wall

Secugrid +

Delta Green

542 t CO2101 t CO2

Angular

retaining wall

Secugrid +

Delta Green

‐68‐ 

Table 3 - Dyke sealing - Rehabilitation of the Kinzig dykes with Geosynthetic Clay Liners (GCL or CBR-C)

(Example DWA Leaflet "Sealing Systems in Dykes" Data [Units] Data [Units] Data [Units] CED [MJ] CO2 [kg]Sealed surface mat measurements  45 x 4,8 m  36000 m²Bentonite mat Bentofix B 4000 installed, surface weight  5.35 kg/m² incl. 6.2 %overlapping (30 cm with a 4,85 m mat width) 5.68 kg/m²Bentonite, removal, transport to the manufacturer Naue   Amount of bentonite per square meter 4,7 kg/m2 incl. 6.2% overlapping  (30 cm with 4.85 mat width) 4.99 kg/m² 179666 kg 2.46 MJ/kg 441978 28747Primary energy content (Feedstock): 47.50 MJ/kg  Manufacture of polypropylene granulate: 0.69 kg/m² 24840 kg 65.50 MJ/kg 1627020 56635Manufacture of polypropylene geomembrane and  material combination (surface weight  650 g/m² incl. overlapping) 0.69 kg/m² 3.6 MJ/kg 89451 16623Manufacture of Bentonite mat 5.68 kg/m² 2.196 MJ/m² 79056 14691Transport to the construction site, distance to the manufacturer's plant i 580 km  204.5 t 1.75 MJ/tkm 207581 16820Installation of Bentonite mat with excavator and wheel loader  36000 m² 3.887 MJ/m² 139932 11339Total of cumulated energy demand  (CED) [MJ] / Total CO2 [t] 2585018 144855

CED [MJ/m²] / CO2 [kg/m2] 71.8 4.0

Table 4 - Dyke sealing - Rehabilitation of the Kinzig dykes with Compacted Clay Liners (CCL)

Data [Units] Data [Units] Data [Units] CED[MJ] CO2 [kg](Example: DWA Leaflet  "Sealing systems in dykes"Surface sealed: 36000 m²Mineral sealing with a medium thickness of  62,5 cm 22500 m³Soil extraction ‐ covering with shovel excavator 22500 m³ 7.6 MJ/m³ 171000 13856Soil transport 45000 t, Transport distance: 35 km 45000 t 2.5 MJ/tkm 3937500 319056Installation with the caterpillar tractor  in  2  to 3 layers of   0,25 ‐ 0,33 m t22500 m³   8.98 MJ/m³ 202050 16372Compacting using a soil compactor in 2 ‐ 3  layers of 0,5 ‐ 0,33 m thicknes 22500 m³ 4.14 MJ/m³ 93150 7548Total CED  [MJ] 4403700 356832CED [MJ/m²] 122.3 9.9

Table 5 - Soil cover for sealing layers (GCL / CBR-C or CCL)

Data [Units] Data [Units] Data [Units] CED [MJ] CO2 [kg]Soil extraction ‐ covering with shovel excavator 36000 m³ 7.6 MJ/m³ 273600 22170Soil transport  57600 t, transport distance: 20 km 57600 t 2.5 MJ/tkm 2880000 233366Installation with the caterpillar tractor in 2  layers of  0,40 m thickness 28800 m³   8.98 MJ/m³ 258624 20956Soil compacting using a soil compactor in 2 layers of  0,40 m thickness 28800 m³ 3.195 MJ/m³ 92016 7456Installation of top soil cover with the long‐arm excavator  d = 0,2 m 7200 m³ 1.97 MJ/m³ 14156 1147Total CED [MJ] 3518396 285096CED [MJ/m²] 97.7 7.9Total CED [MJ] for Bentonite mat sealing and cover  [MJ/m²] 169.5 11.9Total CED  for mineral sealing and cover  [MJ/m²] 220.1 17.8

‐69‐ 

Cover soil

Soil extraction

Transport to construction site

Installation

95,2  MJ/m²

Figure 7 - Comparison of cumulated energy demand (CED) for GBR-C/GCL and CCL dyke

sealing systems.

Cover soil

Soil extraction

Transport to construction site

Installation

7,7 kg/m²

9,9 kg/m²

Figure 8 - Comparison of CO2 emissions for GBR-C/GCL and CCL dyke sealing systems.

‐70‐ 

CONCLUSION

The global demand for reduction of energy consumption and reduced emission of climate related gases like CO2 and CH4 are major challenges for the construction industry as well as other industries.

Economical and ecological advantages based on cost savings and dramatical redcution of

handling of soil masses or "green" solutions by using construction methods with geosynthetics are already well know. A next step to demonstrate ecological advantages is given by comparing two infrastructure construction examples which document that the geosynthetic alternatives have a lower environmental impact due to much less cumulated energy demand (CED) and CO2 emissions. These results are site, product and construction specific. But there is a good chance that the comparison of other construction solutions will show similar advantages. For the future it is recommended to consider the costs of CO2 emission certificates when comparing different offers for a construction job to identify the most suitable solution for the environment.

REFERENCES

DWA Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e.V. (2005): Dichtungssysteme an Deichen. DWA Themen WW-7.3, Hennef. Egloffstein, T. (2009). "Ökologischer Vergleich zwischen Bauweisen mit mineralischen Baustoffen und Bindemitteln sowie Bauweisen mit Geokunststoffen", geotechnik 32 (2009) Nr. 3. Egloffstein, Th., Heerten, G., von Maubeuge, K. (2010): Comparative life cycle assessment (LCA) for clay geosynthetic barriers (GBR-C) versus clay liners and other sealing systems used in river dykes, canals, storm water retention ponds and landfills. Conference proceedings of 3rd International Symposium on Geosynthetic Clay Liners (GBR-C 2k10). Süddeutsches Kunststoffzentrum Würzburg.

EN ISO 14040 (2006). Umweltmanagement – Ökobilanz – Grundsätze und Rahmenbedingungen; Environmental management – Life cycle assessment – Principles and framework (ISO 14040:2006); German and English Version EN ISO 14040:2006, Beuth Verlag Berlin.

EN ISO 14044 (2006): Umweltmanagement – Ökobilanz – Anforderungen und Anleitungen; Environmental management – Life cycle assessment – Requirements and guidelines (ISO 14044:2006); German and English Version EN ISO 14044:2006, Beuth Verlag Berlin.

FFE Forschungsstelle für Energiewirtschaft der Gesellschaft für praktische Energiekunde e.V. (1999): Ganzheitliche Bilanzierung von Grundstoffen und Halbzeugen. Teil I Allgemeiner Teil. Teil II Baustoffe. Teil III Metalle. Teil IV Kunststoffe. München.

Heerten, G., Jackson, A., Restall, S., and Saathoff, F. (2000). "New developments with mega sand containers of nonwoven needle-punched geotextiles for the construction of coastal structures", ICCE 2000 – 27th International Conference on Coastal Engineering, Sydney, Australia, July 2000.

‐71‐ 

Koerner J., Soong, T-Y, and Koerner, R.M. (1998). “Retaining Wall Costs in the USA”, GRI Report No.20, Geosynthetic Institute, Folsom, Penna., June 18, 1998, 38 pages.

SETAC (1993). Guideline for Life Cycle Assessment – A "Code of Practice". Society for Environmental Toxicology and Chemistry, SETAC Workshop held at Sesimbra, Portugal, 31 March – 3 April 1993, Edition 1, Brussels and Pensacola (Florida).

UBA Umweltbundesamt (1999): KEA: Mehr als eine Zahl. Basisdaten und Methoden zum kumulierten Energieaufwand (KEA). Dessau.

‐72‐  

THE USE OF NANOCOMPOSITES TO IMPROVE THE PHYSICAL PROPERTIES OF RECYCLED POLYETHYLENE

Archie Filshill, Ph.D. CETCO Contracting Services Company, Trevose, PA

ABSTRACT

As efforts continue to increase to reduce carbon footprints and create sustainable construction materials, the use of recycled materials is on the rise. A concern with using recycled plastics in construction is the reduced strength of recycled plastics. Nanocomposites have been proven to increase the long term strength of plastics and therefore a potential alternative for geosynthetic applications. INTRODUCTION The preparation of Greenhouse Gas Inventories has become an increasingly formalized and recognized procedure for evaluating the impact of industry and their operations on global warming. These inventories are used to establish goals and identify strategies for the reduction of greenhouse gas emissions. The Kyoto Protocol established a level 7% below the emissions level of 1990 as an initial target for capping emissions, and many institutions have established reduction targets in relation to that standard, for example 10% or 30% “below Kyoto.” More recently such targets have been set as a first step to climate neutrality with initiatives such as the 2030 Challenge, and the President’s pledge. One way to reduce CO2 is the use of recycled plastics. A concern with using recycled plastics in construction or production of geosynthetics is the lower strengths associated with recycled plastics. Plastics become weaker after being re-processed and are therefore limited in their re-use. One way to counter this problem is by the use of nanocomposites during re-processing. By definition, nanocomposites are nanomaterials that combine one or more separate components in order to obtain the best properties of each component (composite). In a nanocomposite, nanoparticles (clay, metal, carbon nanotubes) act as fillers in a matrix, usually polymeric. For this research, nanoclay particles were chosen due to their relatively low cost as an additive to polyethylene. Nanocomposites are prepared by dispersing a modified smectite nanoclay into a host polymer, generally at low levels less than 10 by weight by percent levels. The process is illustrated in Figure 1.

 

This procexfoliatenanoclaymechanicthermopland empcharacterpolymerinanomer looking aby hot-m In generresistancpropertiedirectionsurface dimpermepolymer.increasin NANOC The essewith a plhighly co

Fi

cess is also td. Exfoliatio

y platelets tocal shear olastic and th

ployed are nristics. In soization stagenanoclays i

at nanocompmelt compoun

ral, the addie, structural

es. Because n, exfoliated dimensions eable to gas Nanocomp

ng use in eng

CLAY STRU

ential nanocllate-like struolloidal prod

gure 1 - Sch

termed exfolon is facilitao the point wor heat of hermoset polnecessarily aome cases, the. For other pinto a hot-meposites prepanding.

ition of nanl strength, of the nan

nanomer nanextending toes and liqu

posites also gineering pla

UCTURES

lay bare matucture; see Fiduct of volca

hematic of na

liation. Whenated by surfawhere individpolymerizatlymers, and a function ohe final nanpolymer syselt compounared with sm

nocompositeand therma

nometer siznoclays are t

o one micronuids, and ofdemonstrate

astics (Nanoc

terial is monigure 2. The

anic ash.

‐73‐ 

anocomposit

n a nanoclayface compatidual platelettion. Nanocthe specificf the host pocomposite

stems, procending operatimectite nanoc

es results inal propertiesed dimensiotransparent in, the tightlyffers superioe enhanced cor).

ntmorillonitee bentonite fa

te structure (

y is substantibilization chts can be sep

composites c compatibilpolymer's unwill be prep

esses have beion. For the clays and in

n gains in gs yet withoons of the in most polyy bound struor barrier prfire resistan

e, a 2-to-1 lafamiliar to m

(Nanocor).

tially dispershemistry, whparated fromcan be crelization chemnique chemipared in a reeen developpurpose of

ncorporated i

gas barrier rout significa

individual ymer systemucture in a properties ov

nt properties

ayered smecmost geotechn

sed it is said hich expand

m one anotheated using mistries desiical and phyeactor durined to incorpthis paper winto polyethy

resistance, fant loss in

platelets inms. However,polymer matver the refers and are fin

ctite clay minical engine

to be ds the her by

both igned ysical ng the porate we are

ylene

flame other

n one , with trix is rence nding

ineral eers is

 

Individuadimensioratio. Thsmectite seen in F NaturallyunmodifimodificaconventioCompatib There areaddition novel meion-dipolchemicalNanomerdispersed

Figure

al platelet thons are generhe long axis

can be veryFigure 3.

y occurring ied nanocla

ation, montmonal organicbilized nano

e a number to traditionaeans for modle interactiol complex, wr nanoclay, ad in a polym

2 - Montmo

hicknesses arally 300 to of the partic

y large. The

montmorilloay dispersesmorillonite c polymers.

oclays disper

of chemistrial onuim iondification by

on. Regardlewhich exhiband is suppler matrix, th

orillonite's un

are just onemore than 6cle is usuallprimary sur

onite is hydrs in polymcan be ma. Surface corse readily in

ies to make n modificatioy leaving thess of the

bits a definitlied as a frehey form a ne

‐74‐ 

nique structu

e nanometer 600 nanometly less than rface area ra

rophilic. Sinmers with gade organopompatibiliza

n polymers.

a surface coon there has e sodium iomodificationte gallery spe-flowing, mear-molecul

ure creates a

(one-billionters, resulting1 or 2 μm.

anges from

nce polymergreat difficuphilic and, ation is also

ompatible fobeen a syste

on on the sun technologpacing betwmicronized par blend call

platey parti

nth of a meg in an unusThe specifi50 to 120 m

s are generaulty. Throutherefore,

o known as

or nanoclaysem develope

urface and cogy used, the

ween the platpowder. Whled a nanoco

cle.

eter), but susually high aic surface arm2/g. This ca

ally organopgh clay sucompatible s “intercalat

. For examped and patenoordinating e resulting telets, is cal

hen nanoclayomposite.

urface aspect rea of an be

philic, urface

with tion”.

ple, in nted a it via clay-

lled a ys are

 

Polymer Figure 4.

Layered packet k(diameterhomogenincreases

silicate nano.

silicates areknown as a r/thickness

neously and s in strength,

Figure 3 -

ocomposites

Figure 4

e made up otactoid. Eaon the ordexfoliated a

, flexural mo

SEM image

s incorporate

4 - Nanoclay

of several hach of theseder of 100-as individuaodulus and Y

‐75‐ 

e of a montm

e layered clay

y dispersed i

hundred thine platelets is-1000). Accal platelets thYoung’s mod

morillonite sa

y mineral fil

in polyethyle

n platelet lays charactericordingly, whroughout thdulus and he

ample.

llers in a pol

ene.

yers stackedized by a lawhen the che polymer eat distortion

Nanoclay

Polyeth

lymer matrix

d into an orarge aspect lay is dispmatrix, dram

n temperatur

y Particles

hylene

x; see

rderly ratio

persed matic re are

 

observedbetween surface afollow inNylon 6,as an efftrade-off Also, cregeosynthwhich leshowing type of fresin witand flexu

Fi

Nanocom In this prshows thdiscussed

d at very lowpolymer and

area of the pn permeatin 6 nanocomp

fective way fs.

eep performahetics made ads to collapthe reductio

failure one wth higher iniural modulus

igure 5 - Co

mposite Sam

roject, both nhe samples thd in the later

w filler loadid filler. In ad

platelets greag through thposites by Tto improve

ance is a crfrom HDPEpses of the

on in time to would have titial modulus of HDPE is

mpression c

mple and Te

nanocomposhat were pror section of th

ngs (<10% bddition, barratly increasehe polymeri

Toyota researthe perform

itical factor E experiencesystem and failure by in

to change tous and highes by the addi

reep for a po

esting Progr

site samples duced to teshis paper.

‐76‐ 

by weight) brier propertieed the tortuoic materialsrch group in

mance of a va

in geosynthe deformatiothe ground

ncreasing tho stronger anr creep resisition of relat

olyethylene

ram

of films andst for various

because of tes are greatlyosity of the p. Ever since

n 1993, nanoariety of pla

hetic applicaon and decrabove. Figu

he stress to stnd more expstance. Onetively small

geonet. (Na

d bars were ps properties,

the large sury improved bpath a diffuse the initialocomposites astics withou

ations. Undereases of efure 5 illustratrength ratio

pensive resine way to incamounts of

arejo and All

prepared for, which will

rface area cobecause the sing species l developmehas been vi

ut many pro

er sustained ffective modates this poi

o. To prevenn or find a Hcrease the tenanoclay.

len, 2010)

r testing. Figbe presented

ontact large must

ent of iewed operty

load, dulus, int by nt this HDPE ensile

gure 6 d and

 

Sustainabrenewablrecycled degradatiHDPE dnanocomthose of v In this srecycled compounwas maddesignateflexural p As showcompounrestored nanocomflexural s

bility has bele sources. H

HDPE areions in its u

during geosymposites, it is

virgin HDPE

study, virginplastics. Vi

nding steps bde in nanocoed as HDPEproperties of

wn in Figurnded three tto the level

mposites excestrength in F

(a) Nanoco

Figure 6 - H

ecome a majHDPE is one inferior co

use life. Thisynthetic appls shown thatE.

n HDPE wairgin HDPE being design

omposites wE-3+3% claf all samples

re 7, the tetimes (HDPE of virgin Heeded the va

Figure 8.

omposite film

HDPE nanoco

jor drive towe of the mosompared wis property dlications. Byt the propert

as compoundwas design

nated as HDwith 3, 6 and

y, HDPE-3+s were studie

nsile strengE-3 vs. HD

HDPE. Withalue of the

‐77‐ 

ms (b)Na

omposites fr

wards better st-often recyith virgin Hdegradation hy the same ty of recycle

ded three tinated as HDDPE-1, HDPd 9 weight p+6% clay aed and plotte

gth of HDPDPE-0). Withh 6 and 9% virgin HDP

anocomposit

rom recycled

recycling, rycled plasticsHDPE due has partiallyprinciple fo

ed HDPE ca

imes to mimDPE-0, with PE-2 and HDpercentage oand HDPE-3ed in Figures

PE dropped h 3% clay clay loading

PE. The sam

te Bars

d HDPE.

reduced carbs. However, to the oxid

y limited theor property an be improv

mic propertythe samples

DPE-3 respeof clay and t3+9% clay. s 7 and 8.

by around loading, theg, the tensil

me trend was

bon footprinthe properti

dative and pe use of recyimprovemenved to and a

y degradatios from additectively. HDthe samples

The tensile

3% after be tensile strele strength os observed i

nt and ies of photo ycled nt by above

on of tional

DPE-3 were

e and

being ength of the in the

‐78‐  

Figure 7 - Tensile strength property degradation by repeated compounding and restoration by nanocomposites.

Figure 8 - Flexural strength property degradation by repeated compounding and restoration by nanocomposites.

SUMMARY LLDPE and HDPE are widely used in geosynthetic applications. Properties like tensile strength, flexural strength, puncture resistance, thermal expansion, creep resistance and gas permeability are important material performance parameters in designing geosynthetic materials. By dispersing less than 10% clay into polymer matrix to nanometer level, an effective approach to improve the properties mentioned above is possible. In addition, some property improvement was demonstrated in using recycled plastics as feed stock. The potential application of nanocomposites and nanocomposites from recycled plastics is being explored.

3500

3600

3700

3800

3900

4000

4100

HDPE-0 HDPE-1 HDPE-2 HDPE-3 HDPE-3+3% clay

HDPE-3+6% clay

HDPE-3+9% clay

Tens

ile Y

ield

Stre

ngth

(psi)

-6

-5

-4

-3

-2

-1

0

1

2

3

%ch

ange

Tensile Yield Strength %Change

3800

3900

4000

4100

4200

4300

4400

4500

4600

HDPE-0 HDPE-1 HDPE-2 HDPE-3 HDPE-3+3% clay

HDPE-3+6% clay

HDPE-3+9% clay

Flex

ural

Yie

ld S

treng

t(p

si)

-6

-4

-2

0

2

4

6

8

%ch

ange

Flexural Yield Strength %Change

‐79‐ 

CARBON EMISSIONS OF VARIOUS TYPES OF DRAINAGE PIPE George R. Koerner, Ph.D., P.E., CQA Geosynthetic Institute, Folsom, PA 19033 USA ABSTRACT This paper focuses on the CO2

emissions of various types of drainage pipe. Included are plastic pipe (PVC and HDPE), steel, concrete, and vitrified clay. Of the group, the use and application of plastic pipe in geotechnical applications has the potential to yield significant reductions in carbon emissions compared to other types, as well as substantial savings in cost, time and materials. The relative sustainability for a particular element of any project (like drainage pipe) is assessed by comparing the amount of embodied carbon compared to an alternative design. The concept of embodied carbon provides a measure of cumulative energy required to produce, transport and install the product. By avoiding or minimizing the use of materials with a large carbon footprint (i.e. concrete, steel, quarried stone, etc.), the inherent embodied carbon (carbon dioxide emission) of an overall project can be reduced significantly. INTRODUCTION In the past few decades, plastic pipe has become the material of choice for gas, water and sewage transmission applications. The drainage pipe situation is somewhat lagging but inroads are developing. That said, the plastic pipe industry is well aware of the need to continually improve and implement environmentally sustainable practices. At every stage of the product’s manufacture, use and disposal, the plastics pipe industry is focused on improving sustainable practices and outcomes. In this regard, the two common plastic materials used for civil infrastructure drainage piping are nonplasticized polyvinyl chloride (PVC) and high density polyethylene (HDPE). That said PVC and HDPE materials have come under scrutiny by “green groups”. No real issues have emerged for PE products and much of this scrutiny has been centered on PVC products. Allegations have been made about the environmental performance of PVC products generally. Much of this relates to questioning the safety of plasticizers in flexible PVC products and heavy metal stabilizers used in a wide range of products (typically lead and cadmium). Of note is that PVC pipe formulations do not contain either plasticizers or cadmium. In contrast to the above stated criticisms, plastic piping (both transmission and drainage) has been used for many years and is being used proportionately more than any other pipe. This is due to the many unique qualities. Some of them include the following:

(i) Transportation costs are low: This is due to their lightweight properties. (ii) Low friction losses: Since the surfaces of plastic pipes are very smooth, they require

less energy to transmit fluids compared to other piping systems. Furthermore, they

‐80‐ 

offer less frictional resistance to the fluids flowing through them and help minimize the build-up of scale and other deposits.

(iii) Minimal manufacturing energy requirements: This is in comparison to other materials and there is also minimal increase of energy requirements over the lifetime of the piping.

(iv) Chemical resistance in plastic piping: Plastic piping can be made adaptable to a

wide variety of chemical solutions. In addition, plastic pipes are resistant to corrosive environments and aggressive soils that surround the pipe. They are also resistant to bacterial growth and fungal attack. There is no nutrient host within plastic pipe for either durability concern.

(v) Low thermal conductivity: This has the additional benefit of helping to eliminate or greatly reduce the need for insulation. Another side benefit is that plastic pipe is non-conducting therefore helping to reduce or illuminate corrosion.

(vi) Green benefits: Plastic materials can be recycled

(vii) Popularity: Due to its lightweight nature and its flexibility, plastic piping is becoming more well known and popular among civil engineers in geotechnical, hydraulic and environmental applications. This is particularly the case with the smaller plastic pipes that can be easily maneuvered around and through obstructions.

Figures 1 and 2 shows the dramatic growth of the use of HDPE plastic pipe in the USA and from the perspective of the NYS DOT, respectively. Both sets of data show an exponential rise in the use of HDPE drainage pipe since 1982. One of these factors includes sustainability and specifically the carbon footprint of its manufacture, transportation and installation. That said, the selection of the most appropriate piping material for any project depends on a number of factors, however, this paper addresses only that of CO2 emissions of the various types of drainage pipe materials.

‐81‐ 

$0$200,000,000$400,000,000$600,000,000$800,000,000

$1,000,000,000$1,200,000,000$1,400,000,000

1950

1958

1964

1970

1972

1977

1981

1982

1990

1997

2000

2010

USADollars

Year

Figure 1 - North American HDPE pipe sales. (Ref. PPI)

0

20

40

60

80

1979 1983 1987 1991 1995 1999 2003 2007

PVC

Steel

Concrete

HDPE

Year

Percent Used

Figure 2 – Percentage of drainage pipe used by New York DOT.

PIPE EQUIVALENCY CONSIDERING FLOW CHARACTERISTICS For pipelines that are flowing either full or only partially full like drainage pipe, the Manning equation is generally used.

ν = kn/n R2/3 S1/2 where:

ν = cross-sectional average velocity (ft/s, m/s)

‐82‐ 

kn = 1.486 for English units and kn = 1.0 for SI units A = cross sectional area of flow (ft2, m2) n = Manning coefficient of roughness R = hydraulic radius (ft, m) S = pipe slope (ft/ft, m/m)

Hydraulic radius is expressed as follows:

R = A/P where:

A = cross section area of flow (ft2) P = wetted perimeter (ft)

The volume flow in the channel is then calculated as follows: q = A ν = A kn/n R2/3 S1/2 where: q = volume flow (ft3/s, m3/s) A = cross-sectional area of flow (ft2, m2) It should be pointed out that plastic pipe used for drainage has an extremely smooth interior liner having a Manning coefficient of 0.009 to 0.010. Plastic pipe with perforations in the profile have Manning coefficients in the range of 0.018 to 0.025. See Table 1 for a representation of Manning roughness values representing various pipe surfaces. It is of interest that a pipe flowing slightly less than full can carry more liquid than it can when it is completely full. So assuming for a given situation that the hydraulic radius and slope of a project is the same for all pipe materials the flow would be directly related to the cross sectional area of the pipe and inversely related to the Manning coefficient of roughness. After running a parametric evaluation for several pipe cross sections it was determined that both PVC and HDPE plastic pipes were equal. The concrete, clay and steel pipes ran at a lower flow of about 77%, 67% and 59% of the plastic pipes respectively. Knowing this information along with the Embodied Energy and Carbon Values for Alternative Protection Schemes (ref. U. S. EPA 2005 and University of Bath 2008), one can calculate the total CO2 footprint for each alternative based on the sum of the tons of CO2 generated by each during manufacturing, transportation, and installation. This comparison can be seen graphically in Figure 3.

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Sustainability Comparison of Alternatives

for Drainage Pipe

Option 1 PVC Pipe

Manufacture

Installation

Transport

Total CO2 Footprint

m

COton0.2353 2

m

COton0.0107 2

m

COton0.5388 2

m

COton.7848 2

Option 2 HDPE Pipe

Manufacturer

Installation

Transport

m

COton0.1506 2

m

COton0.0097 2

m

COton0.4499 2

m

COton.6102 2

Option 3 Steel Pipe

Manufacturer

Installation

Transport

m

COton0.3011 2

m

COton0.0164 2

m

COton0.7633 2

m

COton1.0808 2

Option 4 Concrete Pipe

Manufacturer

Installation

Transport

m

COton0.0941 2

m

COton0.0125 2

m

COton.9429 2

m

COton1.0495 2

Total CO2 Footprint Total CO2 Footprint Total CO2 Footprint

Option 5 Clay Pipe

Manufacturer

Installation

Transport

m

COton0.0499 2

m

COton0.0145 2

m

COton.8531 2

m

COton9175.0 2

Total CO2 Footprint

Figure 3 – Comparison of the carbon dioxide generated for five drainage pipe options.

‐84‐ 

The calculations for carbon footprint between the five alternatives are quite profound. Results in Table 1 are in “tons of CO2 emitted per meter of pipe length”.

Table 1 – Comparison of Carbon Emission on Various Types of Drainage Pipe

Alternative Manning Coef. (n)

Materials Only

Fuel Only

Materials and Fuel

Carbon Values (kg CO2/kg material)

Carbon Dioxide Emission

(ton CO2/m) HDPE Pipe PVC Pipe Clay pipe

Concrete Pipe Steel pipe

.010

.010 015 .013 .017

0.0861 0.104 0.0016 0.0012 0.0046

0.505 0.104 0.014 0.015 0.101

0.591 0.553 0.0156 0.106 0.0156

1.6 2.5 0.53 0.21 3.2

0.6102 0.7848 0.9175 1.0495 1.0808

The steel alternative generates the highest CO2 footprint from a materials perspective and the concrete and clay alternative from a fuel perspective. Plastic pipe (PE or PVC) values are much lower in comparison to the others in both materials and delivery. The savings are magnified as the scale of the project increases and also as the transportation distances increases.

The sustainability being focused upon on is a calculation of carbon footprint of various material alternatives. Thus, the amount of carbon dioxide liberated is the major issue. Sustainable living is the latest worldwide trend in lifestyle choices made by people, especially those who have already attained a relatively high level of economic social status. Depending whom you talk to, sustainability means different things to different people. However, it is generally accepted that it is based on a “green” value system that encourages people to live responsible by not using more of the earth’s resources than necessary thus using low carbon footprint materials. Certainly plastic pipe (particularly HDPE) can achieve this goal with respect to drainage piping. In summary, with the growing emphasis on sustainability within the construction industry it is an opportune time to demonstrate how geosynthetic (and particularly plastic pipe) can reduce the carbon footprint of a project when compared to conventional systems. As advocates of geosynthetics it is nice to see that the plastic alternative outperform the conventional options. In addition, drainage systems utilizing plastic pipe can also provide benefits of biodiversity and softer greener options than hardscapes. REFERENCES Koerner, R. M., Designing with Geosynthetics, 5th Ed., Prentice Hall Publ. Co., Englewood Cliffs, NJ, 2005, pp. 2005. University of Bath (2008), “Inventory of Carbon and Energy,” Version 1.6a, see www.carbonneutralfuel.co.uk. U. S. EPA (2005), “Emission Facts,” Office of Transportation and Air Quality, EPA 420-F-05-001, February.

‐85‐ 

You can access documents on greenhouse gas emissions on the Office of Transportation and Qir Quality Web site at: www.epa.gov/otaq/greenhousegases.htm.

For further information on calculating emissions of greenhouse gases, please contact Ed Coe at: U. S. Environmental Protection Agency Office of Transportation and Air Quality 1200 Pennsylvania Ave., NW (6406J) Washington, DC 20460 202-343-9629 E-mail: coe.edmund@epa.gov

‐86‐  

CARBON FOOTPRINT IMPLICATIONS OF THE EROSION CONTROL RESPONSE Sam R. Allen, Vice President, TRI/Environmental, Inc. C. Joel Sprague, Senior Engineer, TRI/Environmental, Inc. ABSTRACT Many geosynthetic erosion control technologies are complete only with a strong marriage to vegetation establishment. Nature’s in-place and well established success in stabilizing surface soils is the cornerstone in almost every erosion control application. The geosynthetic response then, is one of augmentation, stabilization and water management as they encourage, strengthen and reinforce the soil/vegetation matrix and direct flows to desired managed systems. In addition, the partnership of natural materials to geo”synthetic” reinforcement in erosion control materials serves to enhance and extend the functionality of the engineered product. Evaluation of the carbon footprint of these materials begins with an appreciation of the variety of their composite structures, and an awareness of their increasing role in sustainable development. EROSION CONTROL CONTRIBUTION TO SUSTAINABLE DEVELOPMENT Sustainable development is performed under several names and methods. The US Green Building Council (USGBC) has introduced standards that measure environmental soundness. As a national group representing several industries, USGBC compiled the LEED (Leadership in Energy and Environmental Design) Green Building Rating System. This rating and certification system outlines specific parameters that must be met for sustainable development; buildings receive points in several categories. In the stormwater management area, certified LEED buildings must limit the amount of pollutants and manage the rate and quantity of runoff. Techniques used to meet the LEED standards include incorporating geosynthetic erosion control measures, green roofs and rain gardens, building swales and wetlands, constructing parking lots with pervious pavements, and reusing stormwater for irrigation. Using water management systems that incorporate geosynthetics to manage and store stormwater as a resource rather than allowing it to become a nuisance as runoff has brought opportunity for these geosynthetic applications. Perhaps the most significant added value that erosion control products bring to any construction project is in avoided costs. For instance, erosion control using Low Impact Development (LID) techniques that reduce dependence on traditional surface runoff systems and emphasize quick, stable revegetation can produce significant net cost savings. The proper use and application of erosion and sediment controls in LID help to limit the amount of materials used, reduce the amount of re-work for repairs, and help control the extent of the work zone....all of which add value to a project by avoiding costs. The most significant consequence of erosion is loss of topsoil, which hinders the soils ability to support plant life and the many associated benefits of

‐87‐  

mature vegetation. This can lead to additional landscaping costs, and the increased use of fertilizers, herbicides, and other potential pollutants. Runoff and sediments from these sites can carry unwanted nitrogen and phosphorous into the water system causing unwanted plant growth that can change the habitat. In most cases some form of erosion / sediment control will be mandated by the local municipality where construction is planned. There is typically very modest cost incurred when erosion control is implemented at the earliest practical point in a project. Also, erosion control product applications can play a role in achieving LEED certification, and is often mandatory in this regard. Erosion control products may also add sustainability by preventing at least two problems:

(i) if a construction site is in a developed area, the eroding sediment may be going downstream to a location that is negatively impacted by the sediment whether a treatment plant that becomes overloaded, a body of water that becomes clogged, or some fluid transport system that becomes choked, and

(ii) eroding the soils from the original area limit potential future uses of that area.

Both of these are contrary to the elements of sustainability that encourage us to remember there will be others coming after us. Conversely, increased sustainability may be incorporated into a project by using an organic, decomposable erosion control blanket as it may supply a slow release of nutrients for immediate and sustained vegetation growth even in nutrient poor soils and beneficial soil microbes develop that can add long-term structure and stability to the soil and make nutrients available to plants. EROSION AND SEDIMENT CONTROL MATERIALS Erosion control materials cover a broad range of technologies including traditional techniques such as blown straw with sprayed-on tackifiers to rock riprap and cast-in-place concrete. More recent innovations in erosion control include rolled erosion control products (RECPs), hydraulically-applied erosion control products (HECPs), and articulating concrete blocks (ACBs). Similarly there are many types of sediment control materials. Silt fences are a very common perimeter sediment control while synthetically reinforced natural fiber matrices called sediment retention fiber rolls (SRFRs) are used as perimeter controls, slope interrupters, and sediment retention check structures to reduce sediment loss on construction projects. Collectively these materials compete with traditional sediment control barrier structures constructed in-place with rock over a geotextile filter. These different techniques provide different levels of performance and they also represent different associated carbon footprints. In this paper a newer technology, RECPs, will be compared to a traditional technique used for channel linings, i.e., cast-in-place concrete.

 

ROLLED Typicallya varietyThese prsame strgeometryincreasin

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‐88‐ 

UCTS (REC

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‐89‐ 

aped channe

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‐90‐  

The carbon footprint, or CO2 emission, can be described either as the embodied energy and reported as MJ per kg of material or as embodied carbon and reported in kg CO2 per kg of material. The embodied energy value is considered to be somewhat more accurate, but both represent the environmental impact of that material. Table 1 shows the embodied energy and carbon values for a variety of materials used for erosion control. The values generally represent “cradle to factory gate” boundary conditions. Additional carbon footprint must be added to account for transport to the site and material installation. This variety of erosion control materials is significant when considering the carbon footprint implications of erosion product life cycle and use.

Table 1. Life-cycle Carbon Dioxide (CO2) Emission of Materials used in Erosion Control (Values derived from Inventory of Carbon and Energy, Version 1.6a)

Erosion Control Material Embodied Energy - MJ / kg of material

Embodied Carbon - kg CO2 / kg of material

Straw 0.24 0.01 Wood 7.50 0.46

Lightly Reinforced Concrete 1.10 0.127 Stone Riprap 1.00 0.057

Polypropylene 99.20 2.7

CED (CUMULATED ENERGY DEMAND) IN LIFE CYCLE ASSESSMENTS

The multitude of environmental impacts leads to an associated complexity in the data collection process and to complex methods for evaluation. If a large part of the environmental effect results from the provision and consumption of energy, the cumulated energy demand (CED) may be used as a first rough check "short life-cycle assessment". In this way the CED is a first indicator for an evaluation of the energy, transport and material services. Even though the CED also requires data; the energy data may be collected and standardized easily (Hammond and Jones, 2008). The cumulated energy demand (CED) is stated with the units:

• MJ/kg in relation to the product, or • MJ/m3 in relation to the compacted / stabilized soil, or • MJ/m2 in relation to the compacted / sealed surface.

With regard to rolled erosion control products, the polypropylene material has a very high embodied energy and carbon. Concrete and wood have moderately high embodied energy and carbon. And, natural fibers and rock have lower embodied energy and carbon. Natural fiber erosion blankets use a relatively small amount of netting and synthetic PP fiber filled blankets only slightly more. The following illustrates the carbon footprint result of replacing a traditional concrete lining with an RECP.

 

CASE HLINED V A Califorfor a geopollutionwould cahigh costwith the designedsoil whicevents. T

HISTORY: VS RECP-L

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‐91‐ 

CARBON FO

ed its geotheaccess road

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OOTPRINT

ermal operatid. As part

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‐92‐  

The County Public Works Department as well as the Regional Water Quality Control Board were involved with the site design and wanted to assure that the swale had the ability to negate any erosion as well as result in clean water leaving the site. The project contractor superintendent sought alternatives to the concrete swale. After analyzing the project, a RECP lining was selected as a replacement for a concrete-lined design; see Figure 3. The design of the RECP with its three-dimensional permanent netting structure and permanent polypropylene fiber matrix, offered both temporary and long-term erosion control and vegetation reinforcement. By replacing the concrete with a RECP the swale would be able to be vegetated and led to a more aesthetic design as well as easier long-term maintenance. Also since the RECP was a porous product it allowed for water infiltration, thus reducing overall site runoff and eliminating the need for extensive water control. Table 2 demonstrates how the RECP greatly reduced the carbon footprint of the application by reducing the fossil fuel and natural resource consumption.

Table 2 - Carbon Footprint Comparison

Qty Qty Embedded Energy CED (MJ) Total CED

(MJ) Reinforced Concrete Channel Channel Lining Quantity (2300 kg/m3) 89 m3 205000 kg 1.10 MJ / kg 225689 225689 Concrete Transport (to construction site) 20 km 205 t 5 MJ / t km 20500 246189 Placement of Concrete, incl boom truck 89 m3 9 MJ/ m3 801 246990 Total of CED (MJ) 246990 CED (MJ/m2) Unit Cost 281 RECP Channel Channel Lining Quantity (0.728 kg/m2) 878 m2 639 kg 99.2 MJ / kg 63389 63389 RECP Transport (to construction site) 3576 km 0.64 t 5 MJ / t km 11443 74832 Hand Installation of RECP and Stakes 878 m2 0.9 MJ/ m2 790 75622 Total of CED (MJ) 75622 CED (MJ/m2) Unit Cost 86

Note: Transport and installation embedded energy values are estimates.

CONCLUSION The example in this paper summarizes a carbon footprint accounting of a geosynthetic erosion control application within comparison to a hard armor concrete competitive erosion control product. Many more examples are available with even more of a pronounced carbon benefit when compost or natural fiber matrices are employed in rolled erosion control products. Such innovative products play an important role in the continued need for sustainable development achievement, and the associated environmental care.

‐93‐  

REFERENCES 1. Egloffstein, T.A., Heerten, G., von Maubeuge, K.P, Comparative life cycle assessment

(LCA) for clay geosynthetic barriers versus clay liners and other sealing systems used in river dykes, canals, storm water retention ponds and landfills, 3rd International Symposium on Geosynthetic Clay Liners, 2010.

2. Hammond, G. and Jones, C. (2008), Inventory of Carbon and Energy (ICE) Version 1.6a, Univ. of Bath, www.bath.ac.uk/mech-eng/sert/embodied/.

3. Stevens, P.A., How to Calculate the Carbon Footprint of Trucking Shipments, Erzine Articles, http://EzineArticles.com/?expert=Paul_A._Stevens

‐94‐  

GREEN ROOFS WITH GEOSYNTHETICS TO OPTIMIZE SUSTAINABILITY W. Allan Wingfield, AIA Colbond, Inc., Enka, NC, USA ABSTRACT Buildings account for largest percentage of energy use in the United States. According to the Whole Building Design Guide of the National Institute of Building Sciences, on an annual basis, buildings in the United States consume 39% of America's energy and 68% of its electricity. Furthermore, buildings emit 38% of the carbon dioxide (the primary greenhouse gas associated with climate change), 49% of the sulfur dioxide, and 25% of the nitrogen oxides found in the air. (NIBS 2010) The energy use divides into approximately 22% by residential structures and 18% for commercial structures. In the U.S., based on a survey of commercial building energy consumption done by the EPA in 2003, building energy use is responsible for producing carbon emissions of an average of 13 kg (29 lbs) CO2 per square foot of building. In a typical office building the lighting, heating and cooling requirements contribute up to 65% of total energy use. There are a number of different strategies recommended by NIBS to optimize energy use and thereby reduce carbon emissions, such as using renewable energy sources, optimizing system control and monitoring building systems performance (NIBS 2010). One important way is to reduce the energy load requirements of buildings. Green or vegetated roofs have proven to be a very effective method of doing that. Another area green roofs contribute to sustainability is by reducing carbon levels in the atmosphere through carbon sequestration or the removal and storage of carbon. Successful green roofs frequently use a variety of geosynthetics to support a healthy and sustainable vegetated roof. Geosynthetics can contribute in several ways towards the sustainability of the green roof system. Because they are lightweight they reduce structural loading on the building and thereby reduce energy required for the manufacturing, transportation and installation of structural building components. Many geosynthetics can be made of recycled materials which can further reduce the total embedded energy in the materials. GREEN ROOFS FOR REDUCTION OF ENERGY USE Green roofs are one of many building materials and systems that contribute to the overall reduction of building energy use. The largest portion of energy use in buildings is to maintain interior building temperatures. Heat loss in winter and heat gain in the summer through the roof assembly is a significant part of the total heat losses or gains of the entire building envelope. The amount the roof contributes varies because it is dependent on the ratio of roof to wall area. Many larger commercial and industrial buildings in the U.S. have a higher ratio of roof to wall area because they are not multi-storied buildings but have a large building footprint. Roofs inherently receive the largest amount of solar radiation. Roofs do not generally receive the benefit of shading from adjacent trees and other vegetation, which exterior walls receive during certain time periods and seasons of the year. Roof or attic insulation has for many years been the primary means of reducing heat gain or loss, though the roof insulation does not stop the transfer of heat but only slows it down.

‐95‐  

Solar radiation in the cooling seasons of the year raises roof temperatures to very high levels, In certain climates roof temperatures can reach 88° C (190° F). Green roofs moderate roof temperatures. Even green roof systems with a very thin profile have consistently reduced the temperature and fluctuations at the roof membrane surface (Onmura et al., 2001). A study at National Research Council of Canada (NRC) Field Roof Facility (FRF) in Ottawa recorded roof membrane temperatures reaching over 70°C (158°F) in the summer while the membrane under the green roof rarely reached over 30°C (86°F) (Liu & Baskaran 2003). Research was carried out at Portland State University to measure the transfer of heat in different green roof profiles. The study used a variety of planting media depths, moisture content and plant types simulated in a special purpose wind tunnel. Heat transfer was measured as it passed through the green roof profile and roof structure to the conditioned space below. The resultant thermal resistance or mean R-value for the tests was 0.37m²·K/W (2.1 h·ft2 ·°F/Btu). Several interesting findings for representative summertime climate simulations were found. First was that higher air temperatures resulted in an increase of the green roof’s effective R-value because evapotranspiration had a greater contribution to inhibiting heat transfer through the roof. Evapotranspiration on green roofs is a combination of evaporation of water from surfaces such as the planting media but also the conversion of liquid water in plants to water vapor that is released to the atmosphere. The second important finding was that larger leafed plants like clover and vinca, that provide more shading, increased the R-value. It was found that increasing the thickness of the planting media only had a minimal effect on the effective R-value. Increasing the soil depth beyond what was needed to maintain the transpiration requirements of the plants actually reduced the R-value (Bell & Spolek 2009). Energy modeling using the U.S. Department of Energy supported, Energy Plus, shows a 2% reduction in electricity use and a 9-11% reduction in natural gas use for green roofs. A generic 2000 m2 (21,528 ft2) green roof would have an annual savings of 27.2 to 30.7 GJ (7555 to 8527 kWh) of electricity and 9.5 to 38.6 GJ ( 2639 to 10722 kWh) of natural gas (Sailor 2008). The growing problem in dense cities is known as the urban heat island effect. In large cities the air temperature can be 1–3°C (1.8–5.4°F) hotter than surrounding rural areas during the day, and as high as 12°C (22°F) in the evening. The effect is primarily attributed to development using building and paving materials that retain heat and to the reduced amount of shading from vegetation. Green roofs along with cool roofs, cool pavement, and increasing tree and vegetation cover, are all used as part of a strategy to mitigate the heat island effect. HVAC systems of buildings discharge heat into the environment also adding to the elevated outdoor air temperatures. This effect can be reversed through green roofs and other vegetated areas (Mankiewicz, Spartos & Dalski 2009). The EPA has shown that for every 0.6°C in air temperature rise the peak electrical energy loads increase by 2%. (US EPA 2003) A large scale implementation of green roofs to reduce mean air temperature in cities could contribute another 25% reduction in electricity use (Akbari & Konopacki 2005). GREEN ROOFS FOR REDUCTION OF ENERGY USE - A CASE STUDY Four green roof projects south of the Houston, Texas area use green roofs to reduce energy use. All four projects were developed by Jeff Mickler of Jacob White Development and designed by Joe Webb of Webb Architects. Three of the projects have already received U.S. Green Building

‐96‐  

Council’s LEED Platinum certification. The buildings are the twin buildings, 251 & 253 Medical Center in Webster, Texas, the Jacob White Headquarters Building and the Gulf Freeway Office Building; see Figures 1-5. One of the stated goals for of these projects was to reduce energy consumed 50% below that of the owner’s similar office facilities. These buildings are projected to prevent 30 to 54% more green house gas emissions than most conventionally designed commercial office buildings.

Table 1 – Data on the Green Roof Projects near Houston, Texas

Building Sequence GR Square Feet GR Square Meters 251 Medical Center 1 14559 1353 Jacob White HQ 2 11271 1047 253 Medical Center 3 14559 1353 Gulf Freeway 4 15741 1462

The data gathered on these four projects showed the benefit of the evaporative cooling capacity of a green roof, a reduction of solar radiation gain, and a quantifiable means of reducing the tonnage of HVAC system based on reduced loading. Green roofs are classified as intensive, having greater than 15 cm (6 in) of planting media or extensive, having less than 15 cm (6 in.) of planting media. These four buildings are all intensive green roofs with 23-25 cm (9 to 10 in.) of planting media. All of these buildings use multiple strategies for reducing energy use in addition to the green roof. The first building is a three story medical office building whose twin is the third building of the series. In addition to the R-value 71 roof design, walls have an R-value of 24+. The building glazing is one inch insulating glass with low UV transmittance and low emissivity coatings. The building uses a high efficiency, multi-stage air cooled chiller (CFC free) plus variable frequency drive air handlers and electric re-heat at VAV boxes, along with MERV 13 filtration, CO2 monitoring and UV-C light air stream purification treatment. The energy monitoring system installed has continuously monitored the green roof since it has been in place. The 1353 sq. m. (14,559 sq. ft.) green roof mitigates the need for 54 to 61 tons of air conditioning capacity and offsets solar radiation received by the roof equivalent to 65 to 73 tons of capacity. The building electrical power uses 100% alternative sourced energy. The total of all energy reduction methods employed through the construction, equipment, and building operation delivers an energy performance 55% less than a conventional office building. This translates into the prevention of 38,660 kg (85,232 lbs.) of CO2 emissions per month.

 

Figure 1 –

Figur

Figur

– 251 and 25

e 2 – 251 M

e 3 – 251 M

‐97‐ 

53 Medical C

Medical Cente

Medical Cente

Center Green

er Green Roo

er Green Roo

n Roof

of

of

 

The greeseal coaton top of& Drain)(9 in.) inirrigated system hincreasesThe occutemperatubuilding cooling cThe buildfoot mon The Gulfare also ibarrier anvalue of reduces lglazed anbuilding system h

en roof for 2t topped withf this is a dra). Placed onn depth withusing runo

have shown s, but with a upied spaceure below has a roof t

capacity whding is averanth. (Webb 2

f Freeway bimplementednd a spraye

f 26. The valoss of condnd uses 2.5design incluas a calculat

251 Medical h a 1.524 mainage compn top of the h a saturateff water stothat as the lag due to m

e in the buthe roof de

top air cooleile a convenaging 216,002009).

building is thd in this buid 100% waapor barrier ditioned air t cm (1 inchudes balconyted R-Value

Figure 4

Center has mm (60 mil)

osite with a drainage co

ed weight ofored in a ciair temperatmoisture evailding is keeck consisteed chiller whntional build00 MJ (60,00

he fourth anlding to makter borne, csystem allo

through exfih) tinted insy overhangsof 66 (Webb

– Gulf Freew

‐98‐ 

a spray apppolyethylenspecial wate

omposite is f 448- 480 istern. The mture increaseaporation anept at 40°Cently betweehich to date ding would h00 kWh) per

d largest of ke it energy losed cell foows only 0.iltration andsulated glazis that act as b 2010).

way Buildin

plied, water bne heat welder retention fan engineerkg/cu m (2monitoring es, the temp

nd the heat sC (72°F) buen 45.1°Chas not actihave activatr month or 4

f these buildefficient. Th

foam insulati.001 air chad infiltrationing with a solar shade

ng in Sun Sha

based foam ded liner mefabric and fired planting28-30 lbs/cu

of temperatperature of tink of other

ut the greenC- 41.1°C (7ivated more ted 225-250

4.5 MJ (1.25

dings. A numhe exterior wion that givanges per ho. 36% of thelow emissiv

es for the wi

ading

insulation wembrane. Dirilter (Enka R mix of 3.5

u ft). The rotures in thethe soil mixdeeper mois

n roof keep73°F-74°F).than 100 to

0 tons of cookWh) per sq

mber of stratwalls use a ve a minimuour. This gre exterior skvity coating.indows. The

with a rectly

Retain 4 cm

oof is roof

x also sture. s the The

ons of oling. quare

tegies vapor m R- reatly kin is . The e roof

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Table 2 – Insulation Values –Gulf Freeway Building Green Roof (Webb 2010)

Outside air surface at 24 kph(15 mph) wind 5.00Vegetation average depth 8 to 15" (20 - 40 cm)1 used 8" 24.24Average 9" (22.86 cm) soil depth2 used 9" 2.25Drainage medium-EnkaRetain & Drain - air space + filter 1.50 1.524 mm (60 mil) cross laminated polyethylene liner 0.442.03-2.54 mm (80 mil-100 mil) waterproofing membrane 0.4413.3 cm (5 ¼ in) reinforced concrete deck + metal decking3 1.3710.1 cm (4 in) closed cell spray foam insulation4 26.00Inside air surface (still) 5.00

Total R value 66.24

U value 0.015098

1. Value 20-40 cm (7.9 to 15.7") vegetation equates to approximately 15 cm (5.9") mineral wool at 3.03/inch

2. Soils Mechanics Engineering - Thermal Resistance of Earth (eng-tips.com) equates to .25/inch depth

3. R-values tables ESCSI research/tables at .26/inch

4. Manufacturer's tested spray foam insulation installations and testing results for a value of 6.5/inch

The Gulf Freeway building also has an energy monitoring system. The system records roof temperatures with probes 15 cm (6 in.) above the soil surface, at the mid-point of the soil, and at the waterproofing membrane. The air probe has measured temperatures ranging from 30°C to 35°C (87°F to 95°F) , the middle probe typically registers 26°C to 30°C (80°F to 86°F) while the lower probe is consistently in the 25°C to 28°C (77°F to 82°F) range. Roof temperatures on non-green roofs in this region can frequently reach 82°C (180°F). The reduced temperature differential between the roof and the interior space has a significant impact on the HVAC design affecting upfront equipment cost and more importantly on the ongoing life cycle costs. In the peak cooling month of June, equipment loads were reduced by 79 tons or 238,975 Kcal/hr (948,000 Btu/hr) due to solar radiation changes and by an additional 65 tons or 196,625 Kcal/hr (780000 Btu/hr) due to evaporative cooling. The HVAC equipment on the first Medical Center building was conventionally sized to 250 tons, but the actual capacity used to date has never been more than 100 tons. The Gulf Freeway building took advantage of this experience and only a 100 ton unit was installed (Webb 2010).

 

GREEN Any livinthe atmooxygen, carbon dinever halittle opeexceeds 9& Kingsbreservoirbut one th In researcwere estadepth of Sedum aCarbon abiomass Samplingharvestedremovedwere thenground ag C•m-2. 810 g C•entire ext

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sequestered in a green roof could be great improved by changing the planting media depth and composition and by considering other plant species (Rowe 2010). The city of Detroit as an example has approximately 14,734 hectares (36,408 acres) of roof tops. If they were all covered in similar green roofs, 55,252 metric tons (60,904 tons) of carbon could be sequestered in the plants and substrates. This would be equivalent to removing 10,000 mid-sized SUV’s for a year. There is some opinion that green roofs won’t continue to sequester carbon at the same rate over time, however more research needs to be done (Enviro News 2009). RECYCLED RAW MATERIALS IN GREEN ROOF COMPONENTS Recycling is important to sustainability because less energy is needed to produce new products from recycled raw materials than through use of virgin material. As a result less carbon is released into the atmosphere. Use of recycled materials prevents waste and associated greenhouse gas from incinerators. The use of durable geosynthetic materials as components for green roofs reduces need for frequent manufacture of replacement materials. Geosynthetic materials are used in green roofs for drainage, water retention, filters, root barriers, pre-vegetation mats, wind blankets, and planting media stabilization and are typically made of light weight polymers. These products displace the use of heavier aggregates or sand that are sometimes used for filtering and drainage. Much research has been done to develop pre-vegetated green roof mats that allow very thin lightweight growing mats. The mats are currently used in these systems have the lowest green roof system weights available on the market. Pre-vegetated green roofs have been proven over a number of years to sustain vegetation and provide roof temperature reductions similar to green roofs with thicker and heavier layers of planting media. The use of lighter materials results in reduced loading of structural systems which in turn reduces the embedded energy the building structural systems and reduced energy for installation and transport of structural materials. The use of lightweight green roof components also allows installation on existing building stock making older buildings energy efficient and eliminating the energy cost of demolition and building of completely new structures. REDUCTION OF ENERGY REQUIRED FOR REROOFING The typical life of many roof membranes is approximately twenty years. The roofing membrane types used for green roofs are protected membranes similarly protected like inverted roof membrane assembly (IRMA) type roofs or protected roof membranes which place the roof insulation above the membrane. A green roof waterproofing membrane is protected from ultraviolet radiation by the growing media and the vegetation. Ultraviolet radiation breaks down unprotected roof membranes and decreases their practical life. Ultraviolet radiation changes the chemical composition and causes degradation of mechanical properties of bitumen based roofing materials (Liu & Baskaran 2003). A roof membrane will chemically degrade when exposed to pollutants in the air and rain water. An exposed roof membrane is under constant stress from thermal expansion and contraction caused by daytime and nighttime temperature fluctuation as well as seasonal changes. Over time these stresses cause fatigue which break down the membrane and result in failure. Green roofs give protection from direct abrasion and damage

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and will extend the service life of the roof which will reduce environmental impacts and long term life cycle cost (Hoff 2009). The Multnomah Building in Portland, Oregon had a retrofitted green roof installed in 2003. A life cycle cost analysis by Allen Lee of Quantec LLC in August of 2001, helped convince the county government to proceed with the project. One of the compelling arguments was extended roof longevity. The analysis showed that “due to studies on reduction of UV radiation and temperature fluctuations, a green roof would allow the typical roofing membrane to last at least two times longer than a typical membrane.” The study showed the roof would last up to 40 years instead of a normal 20 year period and save the county significant long term capital improvement dollars (King 2004). One of the oldest green roofs in Europe is the Moos Water Filtration Plant outside of Zurich, Switzerland. This roof is one example supporting the longevity of green roof waterproofing, as this roof was installed in 1914 and was first repaired in 2005 (Rowe 2010). The roof is 3.6 hectares (9 acres) in size. The mastic asphalt waterproofing as protected by the green roof lasted 91 years (Werthmann 2007). There have been a number of studies measuring temperatures in different layers of green roof assemblies compared with measurements in a non- green roof control that clearly indicate the tempering of daily recurring temperature swings of the roof membrane (Kumar and Kaushik 2005; Niachou et al 2001; Onmura, Matsumoto and Hokoi 2001; Sonne 2006; Tan et al 2003; Theodosiou 2003). This leads to the conclusion that the life of the roof membrane is increased as a result of the reduction in the waterproofing membrane temperature swing (Bell & Spolek 2009). Because a green roof can extend the life of a roof the energy cost is reduced. This energy cost would include removal of the roof and transportation for disposal. Also the new roof has an additional energy cost for manufacturing roofing components, transporting and installing which are eliminated or deferred. SUMMARY There is a significant potential for green roofs to help reduce the consumption of energy in buildings in North America and to reduce carbon dioxide levels in urban areas. Architects, engineers, developers, and building owners are becoming more aware of the environmental and the economic benefit of implementing green roofs. Green roof projects like the four in the Texas case study are already demonstrating a very short payback time to implement green roofs and other energy reduction measures. As more projects demonstrate the economic sense then environment benefits will be realized on a greater scale, and geosynthetic materials have an important role to play. REFERENCES Akbari, H., Konopacki, S., 2005. Calculating energy-saving potentials of heat island reduction strategies. Energy Policy 2005, 33 (6), 721–56. Bell,H.,Spolek, G.,2009. Measured Energy Performance of Greenroofs, In: Proc. of 7th North American Green Roof Conference: Greening Rooftops for Sustainable Communities, Atlanta, Ga., June 3-5, 2009; The Cardinal Group, Toronto.

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Dunnett, N., Kingsbury, N., 2004. Planting Green Roofs and Living Walls. Timber Press, Inc., Portland, OR.

Enviro News & Business, 2009. Green Roofs for Atmospheric CO2 Capture, October 2009, http://www.enviro-news.com Getter, K.L., Rowe, D.B., Robertson, G.P., Cregg, B.M., Andresen, J.A., 2009. Carbon sequestration potential of extensive green roofs. Environmental Science and Technology 43 (19), 7564-7570.

Hoff, J., 2009. Center for Environmental Innovation in Roofing, New Heat Mitigation and Water Retention Concepts to Expand Green Roofing Demand, In: Proc. of 7th North American Green Roof Conference: Greening Rooftops for Sustainable Communities, Atlanta, Ga., June 3-5, 2009; The Cardinal Group, Toronto. King, J., 2004. Multnomah County’s Green Roof Project: A Case Study. In: Proc. of 2nd North American Green Roof Conference: Greening Rooftops for Sustainable Communities, Portland, OR, June 2-4, 2004. The Cardinal Group, Toronto. Kumar, R., Kaushik, S., 2005. Performance evaluation of green roof and shading for thermal protection of buildings, Building and Environment 40(11): 1505-1511. Liu, K., Baskaran, B., 2003. Thermal performance of green roofs through field evaluation. In: Proc. of 1st North American Green Roof Conference: Greening Rooftops for Sustainable Communities, Chicago, IL 29-30 May 2003. The Cardinal Group, Toronto. Mankiewicz, P.S., Spartos, P., Dalski, E., 2009. Green roofs and local temperature: how green roofs partition water, energy, and costs in urban energy-air conditioning budgets. In: Proc. of 7th North American Green Roof Conference: Greening Rooftops for Sustainable Communities, Atlanta, GA. 3-5 June 2009. The Cardinal Group, Toronto. Niachou, A, Papakonstantinou, K, Santamouris, M, Tsangrassoulis, A & Mihalakakou, G., 2001. Analysis of the green roof thermal properties and investigation of its energy performance, Energy and Buildings 33(7):719-729. Onmura, S., Matsumoto, M., Hokoi, S., 2001. Study on evaporative cooling effect of roof lawn gardens. Energy and Buildings 33: 653–666. Rowe, B., 2010. Green roofs as a means of pollution abatement, Environmental Pollution, 15 October 2010: 1-11. Sailor, D.J., 2008. A green roof model for building energy simulation programs. Energy and Buildings 40, 1466-1478. Sonne, J., 2006. Evaluating green roof energy performance. ASHRAE Journal, Vol. 48, 59-61.

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Tan, P., Wong, N., Chen, Y., Ong, C., Sia, A., 2003. Thermal benefits of rooftop gardens in Singapore, In: Proc. of 1st North American Green Roof Conference: Greening Rooftops for Sustainable Communities, Chicago, IL 29-30 May 2003. The Cardinal Group, Toronto. Theodosiou, T., 2003. Summer period analysis of the performance of a planted roof as a passive cooling technique, Energy and Buildings 35(9): 909-917. U.S. Environmental Protection Agency, 2003. Cooling Summertime Temperatures: Strategies to Reduce Urban Heat Islands EPA 430-F-03-014. Washington, DC. National Institute of Building Sciences (NIBS), WBDG Sustainable Committee, 2010. Whole Building Design Guide, Optimize Energy Use, http://www.wbdg.org Webb, J., 2010. Experiential Design, High Performing Buildings, Fall 2010: 46-54 Webb, J., 2010. Multiplicity and benefits of green roofs: We are just beginning to scratch the surface. In: Proc. of 8th North American Green Roof Conference: Greening Rooftops for Sustainable Communities, Vancouver, BC. 30 November – 3 December 2010. The Cardinal Group, Toronto. Webb, J., 2009. Green roof performance including category 2 Hurricane impacts. In: Proc. of 7th North American Green Roof Conference: Greening Rooftops for Sustainable Communities, Atlanta, GA. 3-5 June 2009. The Cardinal Group, Toronto. Werthmann, C., 2007, Green Roof—A Case Study: Michael Van Valkenburgh Associates' Design for the Headquarters of the American Society of Landscape Architects, Princeton Architectural Press.

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CARBON DIOXIDE EMISSION FOR RIVER DIKE PROTECTION DESIGNS IN SOUTHERN TAIWAN Chiwan Wayne Hsieh, and Jeng-Han Wu National Pingtung University of Science and Technology, Pingtung, Taiwan Liang-Ping Jang, Chao-Chin Hsu, and Ming-Kun Wu 7th River Management Office, Water Resource Agency, Minister of Economic Affairs, Pingtung, Taiwan ABSTRACT The global warming phenomenon has caused frequently observed unusual weather events around the world. Nearly 3000 mm rainfall events were also observed during several typhoons in the last several years in Taiwan. These events induced many floods and catastrophic disasters. Therefore, carbon emission has captured the public attention and government concerns. This paper compares the CO2

emissions for two typical river dike protection designs on the down-stream section. The site is near the ocean in Southern Taiwan. The installation process emitted only about 10% carbon dioxide compared to that associated with the construction materials. The carbon dioxide emission for the design using geosynthetics for river bank protection (second phase) is only about 30% of that associated with the conventional first phase design. Concrete and steel are the major construction materials comprising nearly 90% of the carbon dioxide emissions for both phase designs. In conclusion, the use of geosynthetics for river dike protection significantly reduces carbon dioxide emissions. INTRODUCTION Carbon dioxide emissions have recently received global attention. The use and application of geosynthetics in river dike protection applications has the potential to yield significant reductions in carbon emissions compared to traditional dyke designs, as well as substantial savings in cost, time and materials. The relative sustainability of a particular element of any project (like the traditional reinforced concrete liners) is assessed by comparing the amount of embodied carbon compared to an alternative design like one using geosynthetics. The embodied carbon concept provides a measure of the cumulative energy required to produce, transport and install that product. By avoiding or minimizing using materials with a large carbon footprint (i.e. concrete, steel, quarried stone, etc.), the inherent embodied carbon (carbon dioxide emissions) of an overall project can be significantly reduced. These facts are of interest to the public and government as well. Geography and Climate of Taiwan The island of Taiwan is about 394 km long and 144 km across at its widest point with a land area of 35,879 square km and a total of 1,240 kilometers of coastline. The greater Taiwan area includes the island of Taiwan, the 64 islands of the Penghu archipelago and 20 other outlying islands. Surrounded by seas, Taiwan's coastline is approximately 1,566 kilometers long. Lush

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green hills and mountains occupy two-thirds of Taiwan proper, with the highest elevation being 3,952 meters at Jade Mountain. The Tropic of Cancer (23.5° N) running across Taiwan's middle section divides the island into two climactic zones, tropical in the south and subtropical in the north. The island's average annual temperature is about 24 degrees Celsius in the south and 22°C in the north. The main stream of the northward-moving Kuroshio Current passes up the eastern coast of Taiwan, thus bringing in warm and moist air. Summer and winter monsoons also bring intermittent rainfall to Taiwan's hills and central mountains. As a result, more than 2,500 millimeters of rain fall every year. Ninety percent of this precipitation is observed within the six month rainy season starting from May to October. Background Information of Ton-Kang Creek Pingtung is the southern-most county in Taiwan. The Ton-Kang Creek water collection basin is about 472.2 square kilometers. The river originates from the South Tai-Wu Mountain and flows 44 km through various districts reaching the Taiwan Strait at Ton-Kang district. Flood events were occasionally reported during Typhoon seasons at different locations along the Ton-Kang creek region. The average slope of Ton-Kang Creek ranges from 1/50 to 1/100. The analyzed riverbank protection project is part of the Ton-Kang River Region Management Project. A 50-year flood event is considered in the management project. Conventional Riverbank Protection Design (First phase) The 50-year peak flood capacity is 3510 cubic meters per second in the design section which is four kilometers upstream from the estuary. The project length is about 961 meters. The design section is about 400 meter in width. The average slope is about 1/2500 for the analyzed section. Two phase designs are discussed herewith. The first phase was designed in 2007 and the second phase was conducted in 2008. Multiple functions; such as river bank foundation stability, river dike erosion control and levee top recreation and transportation functions, are considered for the project section. Greater than 30cm in size, rip-rap stone was placed at the bank foundation. Thirty cm thick stepped reinforced concrete slab was then placed to protect the river dike. A brick path for drainage was placed at the top of the levee. A typical cross section is shown in Figure 1. The major construction materials are summarized in Table 1. The typical finished job site photograph is shown in Figure 2. River Bank Protection with the Application of Geosynthetics (Second Phase) In considering reducing the use of reinforced concrete, an erosion control mat was designed to be placed on the front dike slope. Because the design cross section is quite wide, dredged river sand was also used which was pumped and filled in the area between the dike and stone protection area. High strength polypropylene geotextile (55kN/m) was designed as a separator to protect the foundation rip-rap and also placed beneath the erosion control mat. A brick path drainage layer was placed at the top of the levee. A typical cross section is shown in Figure 3. The major

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construction materials are summarized in Table 2. The typical finished job site photograph is shown in Figure 4. Comparison of Carbon Dioxide Consumption The embodied carbon emission data base provided by the Office of Transportation and Air quality was used in this study (U. S. EPA 2005 and University of Bath 2008). One can calculate the total CO2 footprint for each material based on the sum of kilograms of CO2 generated by each during manufacturing, transportation and installation. Carbon dioxide emission based upon the fuel consumption for excavation and placement of on-site soil is also included in the calculation. The carbon footprint calculations between the first phase conventional design and the alternative second phase geosynthetics design are quite straight forward. The quarry stone and subgrade gravel used in this project were transported from a quarry 40 km. from the job site. Carbon dioxide emissions due to transportation are considered in the calculation. Construction equipment, such as the dozer and excavator, consume around 100 liters per working day. The fuel consumption for truck transportation is four kilometers per liter. The dredged river sand is pumped one kilometer from the job site. The total emission results for the major items are summarized in Tables 1 and 2. Please note that the installation process emitted only about 10% carbon dioxide compared to that associated with the construction materials. The energy required and carbon dioxide emissions associated with the excavation and placement of on-site soils is quite similar for both design phases. The only difference between these two phases is the dredging process for the river sand during the installation. However, the carbon dioxide emissions for the design using geosynthetics for river bank protection (the second phase) was only about 30% of that associated with the conventional first phase design. The major difference is the quantity of concrete and steel used during the construction. These two items contributed near 90% of the carbon dioxide emissions for both design phases. In conclusion, the use of geosynthetics for river dike protection is shown to significantly reduce carbon dioxide emissions.

REFERENCES Koerner, R. M., Designing with Geosynthetics, 5th Ed., Prentice Hall Publ. Co., Englewood Cliffs, NJ, 2005, pp. 2005. University of Bath (2008), “Inventory of Carbon and Energy,” Version 1.6a, see www.carbonneutralfuel.co.uk. U. S. EPA (2005), “Emission Facts,” Office of Transportation and Air Quality, EPA 420-F-05-001, February.

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Table 1 - Carbon dioxide emissions of the major construction items for the conventional dike protection design using stepped concrete slab at Ton-Kang Creek, Taiwan (Phase 1)

Item Unit Quantity CO2 per unit (kg)

Quantity of CO2

(kg)

Material

Concrete kg 37,949,664 0.129 4,895,507 Steel kg 575,350 2.750 1,582,213 P.P. Geotextile kg 3,359 2.700 9,069 Erosion Control Mat kg 1,163 2.700 3,140 Quarry stone (φ>30cm) m3 15,059 26.320 396,353

Subgrade Gravel m3 3,276 26.320 86,224

Subtotal kg - - 6,489,929

Installation Excavation m3 85,460 0.540 46,148

Placement m3 54,421 0.540 29,387 Subtotal kg 558,113 Total - - 7,048,042

Table 2 - Carbon dioxide emissions of the major construction items for the alternative dike protection design using geosynthetics at Ton-Kang Creek, Taiwan (Phase 2)

Item Unit Quantity CO2 per unit (kg)

Quantity of CO2

(kg)

Material

Concrete kg 11,120,448 0.129 1,434,538 Steel kg 144,140 2.750 396,385 P.P. Geotextile kg 4,304 2.700 11,621 Erosion Control Mat kg 7,983 2.700 21,554 Quarry stone (φ>30cm) m3 9,016 26.320 237,301

Subgrade Gravel m3 2,482 26.320 65,326

Subtotal kg - - 2,166,725

Installation

Dredged River Sand m3 89,301 1.300 116,091

Excavation m3 64,083 0.540 34,605

Placement m3 64,070 0.540 34,598 Subtotal kg - - 185,294 Total - - - 2,352,019

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9. 84

. 96 41. 5LC

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8

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2

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Subgr ade( t =30cm)Cushi on Sand( t =4cm)

Subgr ade( t =30cm)

AC Pavement ( t =8cm)Concr et e Sl ab( t =30cm)

Cr oss Set i on

Quarry StoneQuarry Stone

Figure 1 - Coventional river dike protection cross section with stepped concrete slab at Ton-

Kang Creek, Taiwan (Phase 1).

Figure 2 - Typical Phase 1 finished job site picture.

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1: 2. 5Top of Di ke6109

Top of Bank

1: 3

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0.50 Sl ope

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Br i ck Si de Wal k

Figure 3 - Alternative river dike protection cross section with the application of geosynthetics at Ton-Kang Creek, Taiwan (Phase 2).

Figure 4 - Typical Phase 2 finished job site picture.

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COMPARISON OF CARBON FOOTPRINTS FOR VARIOUS STORMWATER RETENTION SYSTEMS

Archie Filshill, Ph.D. CETCO Contracting Services Company, Trevose, PA Joseph Martin, Ph.D., P.E. Drexel University, Philadelphia, PA ABSTRACT Construction materials continue to be a major source of greenhouse gases (GHG) based on the fossil fuels used in their production. As the amount of greenhouse gases generated each year continues to increase, there needs to be a more conscious effort to provide alternatives with lower carbon footprints. Geosynthetics have always provided cost effective alternatives to traditional construction materials but now can be shown to provide sustainable alternatives as well. One of faster growing areas within construction is stormwater management. The USEPA mandates storage and infiltration on all new construction projects and leaves the design of these systems to the local engineer. This paper reviews the geosynthetic choices and makes a comparison between the amounts of CO2 generated by each system. Carbon Footprint In the U.S., energy-related activities account for over 85 percent of human-generated greenhouse gas emissions, mostly in the form of carbon dioxide emissions from burning fossil fuels; see Figure 1. More than half the energy-related emissions come from large power plants, while about a third comes from the transportation industry. Industrial processes (such as the production of cement, steel, and aluminum), agriculture, forestry, other land use, and waste management are also significant sources of greenhouse gas emissions in the United States.

Figure 1. U.S. EPA, Inventory of U.S. greenhouse gas emissions and sinks 1990-2008.

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For a better understanding of where greenhouse gas emissions come from, Federal, State and local governments prepare emissions inventories, which track emissions from various parts of the economy such as transportation, electricity production, industry, agriculture, forestry, and other sectors. The EPA publishes the official national inventory of US greenhouse gas emissions and the latest greenhouse gas inventory shows that in 2008 the U.S. emitted slightly less than 7 billon metric tons of greenhouse gases. A million metric tons of CO2 equivalents is roughly equal to the annual GHG emissions of an average U.S. power plant. Naturally occurring greenhouse gases include water vapor, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone (O3). Several classes of halogenated substances that contain fluorine, chlorine, or bromine are also greenhouse gases, but they are for the most part, solely a product of industrial activities. From the pre-industrial era (i.e., ending about 1750) to 2005, concentrations of these greenhouse gases have increased globally by 36, 148, and 18 percent, respectively (IPCC 2007). Figure 2 shows the cumulative change in annual Greenhouse emissions from 1990 to 2008.

Figure 2 – U.S. EPA, Inventory of U.S. greenhouse gas emissions and sinks 1990 – 2008.

As shown in Figure 3, 85.1% of all emissions sources of CO2 come from fossil fuel combustions. It is interesting to note that the drop off in GHG emissions in 2008 is related to the economy. For the purposes of this paper, the focus will be on the amount of CO2 created during the manufacturing of various stormwater retention systems and the amount of CO2 created from diesel fuel consumed during construction.

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Figure 3 – U.S. EPA, Inventory of U.S. greenhouse gas emissions and sinks 1990 – 2008.

Stormwater Retention Systems Stormwater runoff is created from rain events and snowmelts that flow over impervious areas and are not allowed to infiltrate back into the ground and recharge the water table. One of the first controls put on stormwater came through the Clean Water Act, and the National Pollutant Discharge Elimination System (NPDES) permit program. The NPDES permit program controls water pollution by regulating point sources that discharge pollutants into waters of the United States. Most States are authorized to implement a NPDES permitting program. National Pollution Discharge Elimination Systems and Stormwater Ordinances The definition given to NPDES is as follows; “a national program that issues, modifies, revokes and reissues, terminates, monitors and enforces permits that are required when there is a discharge of pollutants” (Dodson, 1999). NPDES permits may be issued for industrial reasons or for construction purposes. A point source discharge is another reason to have a NPDES permit. The EPA defines a point source as follows:

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“…any discernible, confined, and discrete conveyance, including but not limited to any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, landfill leachate collection system, vessel or other floating craft from which pollutants are or may be discharged. This term does not include return flows form irrigated agriculture or agricultural storm water runoff.” (EPA, 1999)

As stated above, the definition leaves the EPA a broad description for a point source discharge so that there can be little defense against saying the site has no point source discharge. NPDES permitting along with public knowledge of stormwater issues led local municipalities to adopt their own stormwater ordinances. These ordinances can control many aspects of the construction design from pipe sizing to maximum amount of impervious cover. With these stipulations on stormwater management, Best Management Practices (BMP’s) are needed to meet or lower current existing conditions. Types of Best Management Practices

Infiltration Beds – Grass swales and porous pavements Filtration – Sand filters, vegetated filter strips, etc. Retention/Detention Basins – Dry ponds, wet ponds and inline storage

Structural BMP’s are defined as any BMP that involves man made structure or alteration that would improve the quality of the stormwater. The huge growth of the stormwater market has created a vast amount of companies and products to meet the requirements and function of structural BMP’s. However, there are a few BMP’s that are used more often than others based on their ease of design and cost. One BMP that is used frequently is the lined retention pond. Retention ponds are inexpensive but take a lot of space and have some negative impacts on the environment due to the exposed standing water. Lined retention ponds have the ability to treat large areas of runoff and reduce the amount of sediment that is released to receiving waterways. An infiltration basin (an unlined retention pond) is another structural BMP that is often used in site development. The infiltration is usually limited to a location that is not near bed rock or foundations. Infiltration basins can handle a high sediment input but must be designed for proper maintenance. The infiltration basin also recharges the groundwater and reduces the volume released downstream. The most widely used systems currently are underground storage systems since they provide the most amount of variability. These systems included stone beds wrapped in filter fabrics, corrugated steel or plastic pipes with a stone envelope around each pipe, half arch plastic modules backfilled with crushed stone, concrete vaults of various sizes and multiple types of plastic cubes used to maximize void space; see Figure 4.

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Figure 4 - (a) Retention Pond (ACF Environmental), (b) Corrugated Metal Pipe (Contech), (c) Arch Chambers (Stormtech®), (d) Conspan® (Contech)

CURRENT PRACTICE The volume of stormwater required to be stored on site continues to increase as impervious surfaces are constructed. Most regulations require the runoff after construction not to exceed the volume of runoff pre-construction. This creates the need for large volumes of storage on site. Traditional storage methods relied on above ground detention and retention basins. These basins require a large footprint. In an effort of optimize the value of real estate there has been a tendency to put the stormwater storage systems underground. This trend is seen more in urban areas where the value of real estate is high and the areas available for development are small. Although there are many types and variations of structural BMP’s including detention and retention basins, this paper will focus on structural BMP’s used for underground stormwater storage. Unlined storage systems will infiltrate and allow captured stormwater to percolate into the subsoil, and offer efficient and economical groundwater recharge. In addition to reducing stormwater flows from the site, recharge systems also present water quality benefits through the soil’s natural filtering ability Corrugated Pipe The most commonly used system to date is corrugated metal pipe (CMP) and Corrugated Plastic Pipe (CPP). The pipe are connected in rows and tied into a manifold for inlet flow as shown in Figure 5.

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Figure 5 - Corrugated Metal Pipe (CMP) (Contech).

Perforated CMP/CPP is installed and typically enclosed with a nonwoven geotextile designed based on site specific soils to prevent clogging. This provides long-term infiltration and protects against soil piping. The system is then backfilled with the specified soil. Standard pipe wall perforations (3/8” diameter holes meeting AASHTO M-36, Class 2) provide approximately 2.5% open area. This provides adequate recharge flow for most soils. There are minimum spacing requirements between pipes to allow for proper backfill enabling the structure to develop adequate side support. The material specified for backfill is usually the state DOT standard which meets or exceeds AASHTO M-145, A-1, A-2, A-3 granular fill. Closer spacing is possible depending on quality of backfill, method of placement and compaction methods. A schematic is given in Figure 6.

Figure 6- Schematic of Corrugated Pipe Storage System (N.T.S.).

Subgrade

Subbase

Pavement 

Pipe 

Backfill – Well Graded

Bedding – Uniformly Graded

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Corrugated Arch Chambers

One of the advantages of arch chambers is that they are flexible and can be configured into beds or trenches of various shapes and sizes. These systems can be installed by hand as shown in Figure 7.

Figure 7 - Installation of Corrugated Arch System (Stormtech®).

These systems require clean angular stone below, between and above the chambers. The storage capacity is calculated by using both the void space within the chambers and 40% porosity within the stone. The chambers are installed with a minimum six inches spacing between each unit and detailed as shown in Figure 8.

This spacing allows for soil arching of the angular stone between arches. The soil arch developed around the chamber provides the structural integrity required to support the pavement system above.

Subgrade

Subbase

Pavement 

Crushed Stone

Arch 

Figure 8 - Corrugated Arch Installation Details.

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Plastic Stormwater Modules

Plastic modules are used as alternates to corrugated pipe and corrugated arch systems. There are over a dozen different manufacturers of plastic modules for stormwater storage. Several examples are given in Figure 9. These systems are the most efficient in terms of voids space. They vary from 90% to 95% void space, are easily assembled in the field, light weight and some are made from recycled materials. The high void ratio reduces the amount of excavation required on jobsite and reduces the footprint required to install. The modular design allows the product to be shipped assembled or unassembled to jobsites to be more cost effective. They are very lightweight and can be installed by hand so heavy equipment is not required. The modular units can be stacked upon each other or installed in various patterns making it easier to work around utilities and other obstructions.

(a) Raintank® (b) Brentwood Industries®

(c) Aquacell® (d) Cudo®

Figure 9 - Various Examples of Plastic Stormwater Modules.

Excavations for the plastic modules are limited to the volume required for storage plus any backfill required by the manufacturer. A typical cross section is shown in Figure 10.

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Figure 10 - Typical Cross Section of a Plastic Stomwater Module.

GeoStorage®

GeoStorage® is a new underground stormwater detention system creates a large storage chamber utilizing geosynthetics, stone and concrete slabs. A geotextile or geomembrane liner system is installed within an excavation. Around the perimeter of the excavation, walls are constructed with geosynthetic reinforcement and open-graded stone to create a large underground chamber. Inlet and outlet pipes extend through the perimeter liner system and wall face into the open chamber. A reinforced concrete roof is installed over the chamber and supported by the perimeter abutment/walls. A schematic of the system is shown in Figure 11.

Figure 11 - GeoStorage® schematic.

Subgrade

Subbase

Pavement 

Plastic Modules 

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Carbon Footprint Calculations

Calculating the carbon footprint of each system requires the breakdown the materials used in the construction of each system and the amount of earthmoving equipment required to install each system. Once the materials are known, a carbon inventory of each material must be calculated. The Department of Mechanical Engineering at the University of Bath in the UK developed the “Inventory of Carbon & Energy (ICE)”. The ICE provides values for the amount of carbon released to produce various materials. It is important to note that the design life of each material must be accounted for as well as the amount of material wasted during production to get a full account of material used. Other factors include what type of maintenance is required for each system. Table 1 lists values used to calculate the carbon footprint.

Table 1 - CO2 Values Used for Calculations

Material kg of CO2/kg of material General Aggregate 0.017

Prefabricated Concrete 0.215 HDPE 1.6

HDPE Pipe 2.0 Polypropylene 2.7

Injection Molded PP 3.9 Recycled Polypropylene 1.4

Additionally, the shipping required for each system must also be part of the calculation.

Diesel fuel for equipment and transportation is 10.1 kg CO2/gallon.

The following assumptions were made for comparative purposes.

All excavated materials remained on site All stone required was delivered from quarry within 30 miles All material deliveries where made within a 100 mile radius All systems are wrapped in a 6.7 oz/yd2 nonwoven geotextile All pipes were designed for infiltration Both CMP and CPP are 48 inch diameter The volume of stormwater storage is 10,000 cubic feet Recycled plastics used 2.5kg less CO2

Each manufacturer provides specific guidelines on the installation of each of their systems. Table 2 was developed using these guidelines and were based on building a stormwater system capable of storing of 10,000 cubic feet of stormwater.

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Table 2 - Comparison of Construction Measures for Each System

System Number of Units

Material Total Weight

(lb.)

Volume of Stone

(yd3)

Volume of Excavation

(yd3)

Equipment (Hours)

Truck Required

for Delivery

Plastic Module

2,253 %-PP 31,531 310 726 58 1

CMP 32 Steel 44,800 402 682 41 4 CPP 32 HDPE 19,200 402 686 41 4 Arch Chamber

134 PP 10,050 580 826 82 1

GeoStorage 8 Concrete 156,240 370 592 40 7

Once the list of materials for each system is calculated and the fuel required to deliver and install the system must be calculated. These values are then used with the data from Table 1 to create the totals in Table 3.

Table 3 - Totals of CO2 Emissions for Each System

Stormwater Retention System Total Amount to CO2 Plastic Stormwater Modules 29,340

Corrugated Plastic Pipe 186,174 Corrugated Steel Pipe 571,227

Corrugated Arch Chambers 28,578 GeoStorage® 25,470

CONCLUSIONS

The results of the calculations for each system show that there can be a vast difference in the amount of CO2 generated depending on what system is selected. The calculations revealed that the type of material combined with the total weight of material used is the significant factor for the total CO2 generated. Steel and Plastics both have relatively high amounts of CO2 in their production that contributes to the overall carbon footprint of the system. Plastics also have high amounts of CO2 in their production, however stormwater modules are more efficient in the amount of material used per unit volume of storage.

It should be stressed that the evaluations did not consider the structural strength of these systems or the cost per unit volume of storage. These factors along with maintenance and system design life should also be considered when evaluating various systems.

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REFERENCES

US EPA Greenhouse Gas Emissions, http://www.epa.gov/climatechange/emissions/index.html  US EPA 2010 U.S. Greenhouse Gas Inventory Report, http://www.epa.gov/climatechange/emissions/usinventoryreport.html  Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990 – 2008: Executive Summary, http://www.epa.gov/climatechange/emissions/downloads10/US-GHG-Inventory-2010_ExecutiveSummary.pdf Hammond and Jones, 2008, University of Bath, Inventory of Carbon and Energy (ICE) Contech Construction Products, DYODS, Design Your Own Detention System

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THE SUSTAINABLE LANDFILL REVISITED

Donald E. Hullings and Hal S. Boudreau III

Jones Edmunds, Gainesville, FL USA

ABSTRACT

In light of the new emphasis on our carbon footprint, this paper revisits the sustainable landfill concept envisioned over a decade ago. The sustainable landfill idea was conceived before its time and became lost in the myriad solid waste management options being proposed in lieu of landfills. While the original concept considered sustainability in terms of a landfill that could be “reused”, it can also be viewed in terms of today’s focus on sustainability and how it relates to greenhouse gas emissions. This paper takes a fresh look at how landfills can achieve our goals for managing waste in an environmentally friendly and cost-effective manner. This paper will explore the greenhouse gas emissions associated with the four stages of landfill operations, how geosynthetics have already improved landfill performance, and how they are the key to eventually fulfilling the promise of a sustainable landfill.

INTRODUCTION

It has been less than two decades since the United States moved from garbage dumps to sanitary landfills with the promulgation of federal “Subtitle D” regulations. Since that time, great strides have been made in landfill technology, particularly the use of geosynthetics as effective replacements of natural materials such as clay and gravel. Even so, the current trend is away from landfills and toward a wide array of more “eco-friendly” alternatives including recycling, waste-to-energy, and composting. Traditional landfills, however, remain the most cost-effective short-term disposal option in most cases. The choice is seemingly not a new one—cost versus environment impact.

Perhaps there is another solution. The promise of the sustainable landfill is to provide a cost-effective and environmentally sound waste management solution by combining green energy production, recycling, and eventual disposal in one operation. The sustainable landfill can effectively use and preserve our valuable resources and minimize impacts associated with greenhouse gases. As this paper shows, geosynthetics play instrumental roles throughout the process.

THE CONCEPT

The sustainable landfill, as envisioned by Environmental Control Systems, Inc. (ECS), is comprised of four stages as shown in Figure 1:

1. Cell Construction 2. Filling cell and Bioreactor Construction 3. Bioreacting 4. Landfill Mining

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Figure 1 – The Sustainable Landfill Concept (ECS, Inc., 2006)

By enhancing decomposition and eventually mining the waste to reclaim airspace, the original concept envisioned a landfill that could be effectively reused. Such a landfill would avoid the costs of future land acquisition, cell construction, and infrastructure, as well as the issues with siting a new landfill. More importantly, the revisited sustainable landfill will focus more on material recovery and power generation than disposal. The use of geosynthetics has already allowed us to reduce our carbon footprint in terms of landfill construction, but the ultimate potential is to use geosynthetics in early collection and control of landfill gases. The stages of the landfill and the key role played by geosynthetics are discussed below.

1. Cell Construction

The sustainable landfill incorporates many of the same advances of the current modern landfill. Figure 2 compares the typical system used in the 1990s and the system most often used in Florida today. Using layers of geosynthetics results in considerable savings not only in construction costs but also in landfill capacity since geosynthetics are much thinner than the earthen layers they replace. The geomembrane/GCL composite is now used more than the prescriptive geomembrane/compacted clay layer and has been shown to have advantages over compacted clay. Advances in high-transmissivity geocomposites allow for shallower bottom grades and/or increased spacing between collection pipes. High transmissivity geocomposites also reduce the head of the liners below that which can be achieved with gravel and are very important when recirculating leachate in the bioreactor process. Geogrids are used to stabilize foundations and sideslopes or in mechanical stabilized earthen berms around the landfill perimeter to further increase capacity. Beyond the cell construction, geosynthetics can be used in other landfill infrastructure—from lining leachate ponds to roadway reinforcement and drainage. Manufactured materials also allow for more reliable and easier construction versus the variability of natural materials.

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The total landfill emission factors reported by the EPA are made up of the following components:

• CH4 emissions from anaerobic decomposition of biogenic carbon compounds;

• Transportation CO2 emissions from landfilling equipment;

• Biogenic carbon stored in the landfill; and

• CO2 emissions avoided through landfill gas-to-energy projects.

Figure 2 – The Traditional Liner and LCRS vs. Geosynthetic Alternative

Although the move to geosynthetics has been largely motivated by financial benefits, the carbon footprint can be greatly reduced when considering the greenhouse emissions resulting from the manufacturing, transporting, and installing the various landfill components. For example, we compared the greenhouse gas impacts from the construction of a typical 10-hectare landfill cell for a prescriptive landfill cell (circa 1993) to that of a landfill of today, located in Florida. We were particularly interested in the greenhouse gas impacts on a per-ton-of-waste basis to get a better idea of the ‘cost’ of disposal. The 10-hectare cell could contain about 1,750,000 m3 of waste or 3,364,000 metric tons, depending on waste density.

The greenhouse gas emissions for the various components are taken from “Emission Facts” (EPA, 2005) with results summarized for our simplified 10 hectare site in Table 1. More detailed information on the various components can be found in other papers presented in “GRI 24 – Optimizing Sustainability Using Geosynthetics.” The original sanitary landfill design (Figure 2) has more layers comprised of soil, which do not have to be “manufactured” and are available locally but still have significant transportation costs because of the sheer volume of material. For our landfill we assumed a haul distance of 30 km for clay and gravel (10 km for soil cover), but this is certainly optimistic for much of Florida. This “soil-rich” base liner and leachate collection system construction emits

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approximately 14,200,000 kg CO2 for the 10 hectares or 4.22 kg CO2 per metric ton of disposed waste.

Conversely the “geosynthetic-rich” alternative emits only approximately 4,560,000 kg CO2 or 1.35 kg CO2 per ton, including manufacturing transportation and installation. In fact, more of the emissions results from the protective soil layer than all of the geosynthetic components combined. Although haul distances are typically much greater for the geosynthetics, much less material needs to be hauled. In our example, we have not counted any increase in airspace as a result the geosynthetic option, but reducing the thickness of the liner and leachate collection system by a few feet can increase airspace by as much as 5 percent. Actual emission values can vary significantly depending mainly on location and the availability of suitable soils, but the conclusion is apparent—although driven primarily by financial savings and increases in capacity, the switch to using geosynthetics in today’s alternative landfill has resulted in a significantly smaller carbon footprint for the same size landfill footprint; see the Appendix for computational details.

Table 1 – Comparison of Construction Greenhouse Gas Footprints

Traditional Bottom Liner 

Material  Total (kg CO2) 

Total (kg CO2/ 

metric tons waste) Compacted Subgrade  2,000  0.00 Compacted Clay (2 ft)  6,068,154  1.80 Geomembrane (PE)  300,000  0.09 

Gravel  2,922,868  0.87 Geomembrane (PE)  300,000  0.09 

Gravel  2,922,868  0.87 Soil  1,676,660  0.50 

Subtotal  14,192,561  4.22 Geosynthetic Bottom Liner 

Material  Total (kg CO2) 

Total (kg CO2/ 

Metric tons waste) Compacted Subgrade  2,000  0.00 

GCL  200,000  0.06 Geomembrane  300,000  0.09 

Drainage Composite (PE)  200,000  0.06 Geomembrane  300,000  0.09 

Drainage Composite (PE)  200,000  0.06 Sand  3,358,321  1.00 

Subtotal  8,784,075  1.35 

2. Filling Cell and Bioreactor Construction

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A vital component of the sustainable landfill is to operate it as a bioreactor. Unlike the “dry-tomb” landfill designed to keep water out, the bioreactor recirculates leachate and adds water as necessary to enhance decomposition. This natural process creates additional landfill capacity, increases the production of methane that is collected and used as fuel, and decreases operational expenses and energy associated with mechanical or manual separation. A bioreactor also stores leachate and may reduce long-term maintenance and monitoring over that of traditional landfills as the decomposition process is condensed and the waste and leachate become more benign. Because distribution of moisture and collection of additional gas are critical in a bioreactor, geosynthetics have additional applications in this process. Drainage composites and pipes can be used throughout the landfill as waste is being placed. Trenches can be constructed in the waste to place pipes, geocomposites, or other drainage materials (Figure 3) or planar system can be placed and covered. Vertical wells can also be constructed after waste is placed to serve as moisture distributors and/or gas collectors.

Figure 3 – Construction of Moisture Distribution Trenches

In reexamining sustainability in terms of impacts to the environment, gas collection and control during the waste-filling process are paramount. Current federal Title V regulations do not require gas collection until 5 years after waste is first placed. Through decomposition, tons of

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greenhouse gases are emitted during that period—orders of magnitude more than the greenhouse gases associated with the liner construction. Approximately half of the landfill gas is methane, which has over 20 times the impact on the environment than CO2. The sustainable landfill provides gas collection and control from the beginning. A gas collection system can be constructed directly below the first lift of waste, and gas can be collected through the leachate collection system. Horizontal gas collectors, pipes, or even geocomposites can be placed over waste lifts as the landfill is being filled. Tarps, which are basically thin reinforced geomembranes, can be placed over inactive filling areas or even placed overnight to help contain gases. While great advances have been made in reducing the impacts of construction, more focus must be placed on containing landfill gases during the filling operation in a truly sustainable landfill. 3. Bioreacting

Although waste decomposes during filling, most decomposition occurs after the cell is filled. As Figure 4 shows, decomposition (measured by gas production) can take decades in a “dry-tomb” landfill. In our 10-hectare cell, peak gas production is 5 times that of a traditional landfill and a bioreactor can accomplish the majority of decomposition within years. The previous emphasis of the sustainability landfill was to enhance decomposition to reclaim the airspace. Today’s focus is on containing the gas to reduce emissions and generate green power. An average landfill emits 1150 kg CO2e/metric ton—three orders of magnitude greater than the construction impact of our geosynthetic liner system. However, landfills that incorporate a good cover, have a gas recovery system, and generate electricity can have zero net emissions (EPA, 2006). A geomembrane cover with horizontal gas collection can collect 99% of the methane that would have escaped the landfill (Van Kolken Banister, 2010). The single greatest way to optimize sustainability in terms of reducing our carbon footprint is to decrease emissions from decomposition.

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Figure 4 – Landfill Gas Curve

At this stage, an exposed geomembrane cover (EGC) is an ideal cover system (Figure 5). In addition to containing the methane gas, an EGC contains potential seeps of leachate and controls odors and vectors. At half the cost of traditional covers (Koerner, 2011), an EGC also eliminates concerns regarding the stability and erosion of soil covers and provides more operational flexibility such as adding wells and moving pipes since the geomembrane is not covered with soil. Also, much like the cost for the liner construction, the emissions from the construction of an EGC can be much lower than a traditional cover. The addition of solar panels on the EGC can be another source of green energy.

Figure 5 – EGC at Polk County North Central Landfill

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4. Landfill Mining After bioreacting, the landfill is mined to recover the usable materials—de facto recycling. The organic component of the waste has been greatly reduced, which facilitates easier separation and sorting. The waste can be excavated and screened (Figure 6), and the larger particles (“overs”) can processed to recover valuable recyclables.

Figure 6 – Landfill Mining and Screening

The smaller particles (“unders”) from screening can be placed in the new cell as daily or intermediate cover for further decomposition, possibly processed further into a compost or another use in the future. Delaying the processing of the harder-to-recycle materials such as plastics until the landfill mining stage may allow the recycled markets time to develop more than today to provide greater revenues per ton and allow a wider variety of materials to be effectively recycled than can be done currently. Future technologies may also provide even more options for the economic and environmentally sound use of the residuals and recycled materials. Valuable resources are not discarded in the sustainable landfill but are simply stored to use in the future., geosynthetics can be used during this stage as temporary cover for stormwater and odor control during the mining process. OVERALL IMPACTS OF THE SUSTAINABLE LANDFILL We have examined the sustainability for each stage of the operation, particularly in regard to greenhouse gas emissions, but there are also some overall benefits. Going back to the original concept, the lined cells can be reused after mining, so impacts of future landfill construction are dramatically reduced. By offering the benefits of waste-to-energy, composting, and recycling in one facility, multiple trips to different facilities and the associated emissions can be eliminated. Significant barriers to other technologies, such as large capital costs for waste-to-energy plants or poor markets for some recyclability materials, are eliminated in the sustainable landfill. Traditional landfills are usually the most cost-effective means of disposal, but the sustainable landfill can be just as cost-effective while also being carbon neutral.

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As shown in the figure below the EPA emission factors can vary greatly depending on the capture and energy production. As shown in the last bar on the right, a landfill that employs an active gas collection system and produces energy can have a net zero or even negative carbon footprint.

SUMMARY AND CONCLUSIONS The application of geosynthetics in landfill designs has resulted in significant savings in construction costs and capacity. Although not the primary intention, the use of geosynthetics has significantly reduced the carbon footprint. Impacts can vary dramatically and are certainly site specific, but greenhouse gas emissions can easily be cut in half and perhaps even more. At this stage, we have done what we can to reduce the construction footprint, but the key to overall emissions lies in the cover. In a broader view, using geosynthetics during landfill filling to enhance gas collection and constructing a geomembrane cover to contain gases after filling are the critical elements to reduce emissions. The sustainable landfill, with a geosynthetic cover and operating with landfill gas recovery and electricity generation, can result in a carbon-neutral landfill. REFERENCES ECS, Inc. (2006), “Full-Scale Application of an Aerobic Landfill Bioreactor System,” Proceedings 11th Annual SWANA Landfill Symposium, Nashville, SWANA Publication. Koerner, R. and Geosynthetics Institute (2011), “Traditional Versus Exposed Geomembrane Landfill Covers: Cost and Sustainability Perspectives,” Proceedings GRI-24 Conference, Houston, GSI Publication, Folsom, PA. U. S. EPA (2005), “Emission Facts,” Office of Transportation and Air Quality, EPA 420-F-05-001, February. U.S. EPA (2006), “Solid Waste Management and Greenhouse Gases: A Life-Cycle Assessment of Emissions and Sinks,” ICF International for EPA, see http://epa.gov/climatechange/wycd/waste/SWMGHGreport.html#sections. Van Kolken Banister, A. and Sullivan, P. (2010), “LFG Collection Efficiency: Debunking the Rhetoric,” MSW Management, Vol. 20. No. 4, pp. 26-32.

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Appendix – Sustainable Landfill Carbon Footprint Comparison

Landfill GeometryCell Size = 10 Hectare 24.71 acres

100,000 m2 1,076,391 ft2

Cell Height = 45 m 148 ftSideslope = 3 :1 3 :1Landfill VolumeVolume = 1,750,000 m3 2,288,914 CY     Base Width = 316.23 m 1,037 ft     Top Width = 46.23 m 152 ftLandfill TonnageTonnage = 3,364,127 ton (metric) 3,051,885 tonUnit Weight = 0.52 ton(metric)/m3 0.75 ton/CYHaul DistanceDirect Haul Distance = 10 km 6 miTransfer Trailer Distance = 40 km 25 mi

Proof Rolling 200 10 2,000Soil Foundation Layer 70,000 10 700,000Geotextile 20,000 10 200,000GCL 20,000 10 200,000Geomembrane (40 mil PE) 20,000 10 200,000Drainage Composite (PE) 20,000 10 200,000Protection Soil 288,000 10 2,880,000Topsoil 227,000 10 2,270,000Seeding and Vegetation 200 10 2,000Subtotal 6,654,000

Compacted Subgrade 200 10 2,000Compacted Clay (2 ft) 606,817 10 6,068,165Geomembrane (60 mil PE) 30,000 10 300,000Gravel 292,287 10 2,922,868Geomembrane (60 mil PE) 30,000 10 300,000Gravel 292,287 10 2,922,868Soil (1') 167,666 10 1,676,660Subtotal 14,192,561

Proof Rolling 200 10 2,000Soil Foundation Layer 70,000 10 700,000Geotextile 20,000 10 200,000GCL 20,000 10 200,000Geomembrane (60 mil PE) 30,000 10 300,000Subtotal 1,402,000

Compacted Subgrade 200 10 2,000GCL 20,000 10 200,000Geomembrane (60 mil PE) 30,000 10 300,000Drainage Composite (PE) 20,000 10 200,000Geomembrane (60 mil PE) 30,000 10 300,000Drainage Composite (PE) 20,000 10 200,000Soil (2') 335,332 10 3,353,321Subtotal 4,555,321

Aggregate 0.005 0.215Cement 0.830 0.045Clay Pipe 0.530 0.023Compacted Soil (2 ft) 0.023 2.700Concrete 0.129 2.450Drainage Composite (PE) 1.700 0.005Geomembrane (PE) 1.750 0.190Geosynthetic Clay Liner 0.220 0.023Geotextile (PP) 2.700 2.750HDPE Geosynthetic 1.600 0.056

Total(kg CO2/metric tons waste)

0.00

Geosynthetic Bottom Liner

Unit Footprint(kg CO2/ha)

Area (ha) Total (kg CO2)

0.00

Total(kg CO2/metric tons waste)

1.98

4.22

Traditional Bottom Liner

1.800.09

1.35

0.060.090.06

Material

Total (kg CO2) Total(kg CO2/metric tons waste)

0.21

Traditional Cover

MaterialUnit Footprint(kg CO2/ha)

Area (ha) Total (kg CO2)

Material Unit Footprint(kg CO2/ha)

Area (ha) Total (kg CO2) Total(kg CO2/metric tons waste)

Material Unit Footprint(kg CO2/ha)

0.870.50

1.00

0.42

0.000.060.09

0.09

0.210.06

Data

Geosynthetic Alternative Construction CalculationsExposed Geosynthetic Cover

Area (ha)

0.860.670.00

0.00

Traditional Construction Calculations

Material Kg CO2/Kg of Material

0.060.09

EPA Emission Values

0.87

0.060.060.060.06

Prefabricated ConcreteProof RollingProtection SoilPS Geosynthetic

Kg CO2/Kg of 

Material

SteelStone

PVC GeosyntheticSand

Seeding and VegetationSoil Foundation

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SUSTAINABILITY CONTRIBUTION BY MSE BERMS AT LANDFILLS Douglas N. Brown Tensar International Corporation, Alpharetta, GA USA Willie Liew Tensar International Corporation, Alpharetta, GA USA ABSTRACT Mechanically-stabilized earth (MSE) berms are increasingly utilized by landfill Owners to efficiently create usable airspace for waste disposal. Since their inception in the late 1980’s, MSE berms at landfills have contributed to sustainability by simultaneously allows geometric maximization of the volume of usable airspace within a given permitted footprint while minimizing the carbon footprint of the berm construction operation, by eliminating or delaying the need to site and construct new waste containment facilities, and by requiring less time and resources to construct versus conventional containment berms.

This paper will offer a brief historical perspective on MSE berms in waste containment facilities and establish prevalence of their use by solid waste landfill Owners, identify the benefits of MSE berms relative to sustainability, and finally will quantify conceptually the benefit, in terms of carbon footprint, of an MSE berm versus a traditionally constructed, unreinforced one. Future considerations of MSE berms at landfills that could further sustainability are also discussed. BACKGROUND – MSE BERMS

Mechanically stabilized earth (MSE) technology consists of utilizing geosynthetic or metallic reinforcing elements in combination with soil and a wide selection of facing elements to create safe, cost-effective grade separations for highways, civil earthworks and, as in the focus of this paper, waste containment facilities. The first geosynthetically-reinforced grade separation structure worldwide was completed in France in 1971 (LeFlaive, 1988) and in North America in Oregon in 1974 (Greenway et al. 1999).

In 1985, MSE technology was used for the first time in North America to create useful airspace within a waste containment facility (Seawell and Mattox 1987). At this chemical facility near Mobile, AL, high-density polyethylene (HDPE) geogrids were used as primary reinforcement in combination with polypropylene (PP) geogrids as intermediate reinforcement to create an over steepened 1H:1V slope 2.5 meters in height, resulting in 250,000 cubic meters of airspace. This solution was achieved in two months and at only 25% of the cost of a new facility. The same facility was later subject to a second 0.9 meter vertical expansion which added an additional 75,000 cubic meters of airspace and consisted of near-vertical construction utilizing the same primary reinforcing with a facing consisting of welded wire forms (WWF) and polypropylene facing geogrid.

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MSE technology using geosynthetic reinforcing was introduced to the municipal solid

waste market in 1996, with the design and construction of the first MSE berm at Pottstown Landfill in Pottstown, PA (Ballod and Brown, 2008). Since 1996, MSE berms have been constructed at 11 different landfills in Pennsylvania alone, with additional construction occurring in New York, Georgia, Maine, New Hampshire, Delaware, Maryland, Massachusetts, Florida, Alabama, Louisiana, Virginia, and Kentucky. A recently constructed MSE berm is shown in Figure 1.

Figure 1. Recently Constructed MSE Berm at Landfill

Continued use of accepted design guidelines, along with a preponderance of literature

on all aspects of MSE berms, including stability (Luettich and Quiroz 2008; Qian and Koerner 2009) and construction aspects (Brown and Ballod 2008), have created an environment in which the use of MSE berms may continue into the foreseeable future.

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MSE BERMS AND SUSTAINABILITY

Current solid waste management strategy is commonly comprised of waste minimization, collection, transfer and treatment, and disposal components (Barron 2001). Disposal of solid waste in productive manners, such as composting, anaerobic digestion and waste-to-energy accounts for only a fraction of the overall waste stream, leaving the remainder to be landfilled. In fact, although the disposal percentage of waste landfilled decreased from 89% of the total in 1980 to 54% in 2008, 135 million tons of all MSW generated was landfilled in 2008 (USEPA 2009). Therefore, the disposal component of the overall solid waste stream remains influential with regard to environmental sustainability. It is in construction of the containment features of the modern solid waste disposal facility that MSE berms contribute to sustainability.

Wikipedia defines sustainability as “the ability to endure.” Less broadly but more pertinent, the United States Environmental Protection Agency defines sustainability as “the ability to achieve economic prosperity while protecting the natural systems of the planet and providing a better quality of life for its residents.” (Collin 2006). Within the latter definition, it is proposed herein that the use of MSE berms at waste containment facilities leads to several sustainability benefits, including:

Reduction of carbon footprint by allowing geometric maximization of the volume of usable airspace within a given permitted footprint – as shown in Figure 2 below, the use of MSE berms at a landfill can generate the maximum volume of airspace within a permitted footprint.

Figure 2. MSE Berm Used as for Containment at Landfill

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Or, put in other terms, because the footprint of the containment berm is minimized, the volume of usable airspace is maximized. As a result of this footprint minimization, the impact as quantified in terms of carbon footprint is also minimized. A simple quantification of the carbon footprint reduction offered by MSE berms is demonstrated in the example presented later in this paper. An additional sustainability benefit associated with MSE berms originates from the vegetated face used with most berms (Figure 3). The vegetation serves to reduce the carbon footprint of the containment berm by acting as a natural filter removing atmospheric carbon dioxide.

Figure 3. Vegetated Face of MSE Berm at Landfill Ultimately the use of MSE berms at a site must consider all factors that impact their

use, including many economic ones (Dickson et al. 2008). For sites at which airspace maximization or carbon footprint minimization is important, MSE berms can be an effective tool.

Elimination or delay in need to site and construct a new facility – in many cases, the use of MSE berm technology has created years of new airspace within the footprint of an existing facility, thereby delaying construction of a new facility. In addition to maximizing

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the efficiency with which the additional airspace is created, this scenario eliminates disturbance of greenfield sites or other previously undisturbed, natural habitats. Whether quantified in terms of carbon footprint or any other indicator, this is a sustainability benefit.

Reduction in time and resources required to construct a given containment berm configuration – irrespective of the airspace considerations at a site, many containment berm configurations can be constructed more efficiently, in terms of time and resources used, using MSE berm technology. Since carbon footprint is a measure of greenhouse emissions per unit of time, decreased construction time inherently leads to reduced carbon footprint. Although this benefit is dampened on sites where adjacent land is inexpensive and/or time is not a factor, most sites do not have these luxuries. QUANTIFICATION OF SUSTAINABILITY IMPACT AS MEASURED IN CARBON FOOTPRINT

The Clean Air Act defines the US EPA’s responsibilities for protecting and improving the nation’s air quality. Currently the EPA is considering how best to impose new regulations on industry regarding industry’s annual emission of greenhouse gases (GHG). One measure of emission of GHG’s is commonly referred to as “carbon footprint” since carbon dioxide is a primary GHG emitted in industrialized countries.

The sustainability benefits offered by MSE berms at landfills were presented qualitatively above. Quantification of these sustainability benefits in terms of carbon footprint can be complicated and difficult, since some factors such as the value of undisturbed natural habitats and reduction in time and resources required are not easily quantified.

However, a simplified calculation can be performed to quantify the benefit of MSE Berms compared to traditional landfill expansion even without consideration of the major contributions described above. Quantification can be made by considering the carbon footprint of the materials and the associated material transportation required to construct a traditional unreinforced perimeter berm with 3H:1V side slopes (Figure 4) and an MSE Berm with a steepened 0.5H:1V exterior side slope (Figure 5). This calculation assumes that the construction will be based on that of a new landfill cell (rather than retrofit), a berm height of 12.2 m (40 ft), and that the liner materials are the same between the two options. Construction of a traditional berm requires select backfill to be transported and compacted. In addition to the select backfill and compaction components, materials required for construction of an MSE berm include HDPE primary reinforcement, PP geogrid face wrap and WWF facing with support struts. The materials and the associated carbon footprint for the two options are presented in the flow chart shown in Figure 6. The total carbon footprint (materials and transportation only) of constructing a traditional unreinforced perimeter berm is 200.3 kgCO2 per square foot while the total carbon footprint of constructing a MSE berm is 133.9 kgCO2 per square foot. The carbon footprint is therefore 33% less with an MSE Berm as compared to the traditional approach.

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Figure 4. Traditional 3H:1V Unreinforced Perimeter Berm

Figure 5. MSE Berm with 0.5H:1V Exterior Slope

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Figure 6. Flow Chart Comparing the Carbon Foot of MSE Berm and Traditional Berm

Traditional 3H:1V Berm or 1H:2V MSE Berm

Option 2 1H:2V MSE Berm

Option 1 Traditional 3H:1V Berm

Compacted Select Fill Compacted Select Fill

Import of Select Fill (Transportation)

Total CO2 Footprint 200.3 kg per ft2

Import of Select Fill (Transportation)

HDPE primary reinforcement, PP face wrap and WWF with strut

facing materials

Material Shipping for MSE Berm (Transportation)

Total CO2 Footprint 133.9 kg per ft2

182.6 kg/ft2

17.7 kg/ft2

117.4 kg/ft2

11.4 kg/ft2

4.7 kg/ft2

0.4 kg/ft2

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FUTURE CONSIDERATIONS

The benefits listed above suggest that use of MSE berms at landfills may create sustainability benefits for landfill Owners for some time to come. Additional future considerations include:

• Beneficial re-use of waste stream as fill for MSE berm – re-use of materials such as coal combustion products (CCP’s) like bottom ash and fly ash, would positively impact the sustainability benefit, since what would have ended up as part of the waste stream would instead be used to create airspace. The controlled construction techniques commonly used to construct MSE berms are ideal for use of CCP’s, which commonly must be hydrologically isolated. Pending changes to the regulations regarding CCP’s promise to not only increase pressure on the airspace decisions made by landfill Owners, but also increase the scrutiny under which these materials are handled – ultimately these changes will magnify the sustainability benefit. This approach has been successfully utilized on at least two landfill projects in the US to date.

• As previously described, the MSE berm approach utilizes a near-vertical component

made possible by utilizing geosynthetics in composite with soil. One sustainability benefit possible with MSE berms is to take advantage of this near-vertical surface to suspend alternative energy technologies such as solar panels. If this GHG-free method of energy production is used to replace conventional means, the sustainability benefit would be measurable and significant. This approach has been used successfully on at least one landfill project in the US.

CONCLUSIONS

This paper provides a brief historical perspective on the application of MSE berms at landfills and establishes the prevalence of MSE berms in current solid waste management construction. Contributions by MSE berms to sustainability are identified qualitatively and then supported quantitatively on the basis of reduced carbon footprint. Future considerations are also discussed. ACKNOWLEDGEMENTS

The authors wish to thank Dr. Robert Koerner for data he shared on the carbon footprint of common geotechnical and geosynthetic materials. The authors also wish to acknowledge Joseph Rogers, Senior CAD Operator at Tensar International Corporation, for his efforts in developing the figures used in this paper. REFERENCES Ballod, C. and Brown, D. (2008). “Mechanically Stabilized Earth Berms: Overview at Pennsylvania Landfills”, Proc. 2008 Global Waste Management Symposium, Copper Mountain, CO.

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Barron, J.M. (2001). “Environment, Construction and Sustainable Development, Vol. 2, John Wiley & Sons Ltd., New York, pp. 437-444. Brown, D. and Ballod, C. (2008). “Construction Details and Related Considerations of MSE Berms at Landfills”, Proc. 2008 Global Waste Management Symposium, Copper Mountain, CO. Collin, R.W. (2006). The Environmental Protection Agency – Cleaning Up America’s Act, Greenwood Press, Westport, CT, USA, pp. 250-253. Dickson, J.R. and Soong, T.Y. (2008). “Economic Benefits of Using Engineered Berms”, Proc. 2008 Global Waste Management Symposium, Copper Mountain, CO. Greenway, D., Bell, J.R., and Vandre, B. (1999). “Snailback Wall - First Fabric Wall Revisited at 25 Year Milestone”, Proc. of Geosynthetics ’99, IFAI, Vol. 2, Boston, Massachusetts, USA, April 1999, 905-919. Leflaive, E. (1988). “Durability of Geotextiles: The French Experience”, Geotextiles and Geomembranes, Vol. 7, Nos. 1-2, 23-31. Luettich, S. and Quiroz, J. (2008). “Landfill Stability Analyses for the Application of Mechanically Stabilized Earth (MSE) Perimeter Berms”, Proc. 2008 Global Waste Management Symposium, Copper Mountain, CO. Qian, X. and Koerner, R.M. (2009). “Stability Analysis When Using an Engineered Berm to Increase Landfill Space”, J. Geotech. And Geoenviron. Engr., Vol. 135, No. 8, August, pp. 1082-1091. Seawell, H and Mattox, R.M. (1987). “An Economical Solution to Increasing the Capacity of an Industrial Waste Facility with a Geogrid Reinforced Dike”, Proc. Geosynthetics ’87, New Orleans, USA, pp. 341-352. U.S. Environmental Protection Agency (2009). “Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2008”, EPA-530-F-009-021, US EPA, Washington, DC.

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CARBON FOOTPRINT COMPARISON OF GCLs AND COMPACTED CLAY LINERS Christos Athanassopoulos, P.E., CETCO Richard J. Vamos, Ph.D, P.E., DAI Environmental, Inc.

INTRODUCTION

Geosynthetics are playing an increasingly more important role in environmental and geotechnical applications, as local sources of natural barrier and drainage materials diminish. While much work has already been devoted to comparing the technical effectiveness of geosynthetics to natural soils, there has been little study into the comparative energy efficiencies and sustainability of geosynthetics and soils. Accordingly, the purpose of this study is to compare the carbon footprint (or equivalent greenhouse gas emissions, in kg of CO2 equivalents per hectare) of a natural compacted clay liner (CCL) with a geosynthetic clay liner (GCL). Specifically, the analysis looked at the following bottom liner options for a hypothetical RCRA Subtitle D municipal solid waste landfill:

Option 1. Prepared subgrade, 0.6-meter thick compacted clay liner with a hydraulic conductivity of 1 x 10-7 cm/sec, 1.5-mm HDPE geomembrane, and sand drainage layer. This is the prescriptive Subtitle D liner system.

Option 2. Prepared subgrade, GCL, 1.5-mm HDPE geomembrane, and sand drainage layer. This is a commonly used alternative to Option 1.

Each of these liner system options is discussed separately below.

COMPACTED CLAY LINERS

Compacted clay liners been historically used as barrier layers in waste containment facilities to either limit the infiltration of surface water into the buried waste (caps) or limit the migration of leachate into the environment (bottom liners). Common regulatory requirements for compacted clay liners are a minimum thickness of 0.6-meters, with a maximum hydraulic conductivity of 1 x 10-7 cm/sec. Off-site borrow sources of clay or silt soils are often required to construct a low-permeability compacted soil liner. Significant upfront investigation is necessary to properly characterize the extent and the quality of the soil at the borrow source. Emissions associated with upfront investigation and characterization of the borrow source are not being included in the carbon footprint analysis.

As discussed by Daniel and Koerner (2007), in some cases, soils from the borrow source are clay-deficient, requiring the addition of bentonite to produce a compacted soil liner that meets the required hydraulic conductivity. For the purposes of this analysis, a “best-case” scenario is assumed, where the soil from the borrow pit has a high enough fines content and plasticity index to meet the hydraulic conductivity requirements without any amendments.

Clay at the borrow source is excavated using standard construction equipment, which also loads the material onto tri-axle dump trucks for transport to the job site. Each truck is assumed to have a capacity of 15 m3 of loose soil. Using a compaction factor of 1.38, it is estimated that over 550 truckloads of soil would be needed to construct a 0.6-meter thick compacted clay liner over a one-hectare area.

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The distance from the borrow source to the job site is, of course, site-specific and can vary greatly. For the purposes of this analysis, a distance of 16 km (10 miles) was assumed. Since transport from the clay borrow source and the job site is such a large component of the overall carbon emissions, the sensitivity of the overall carbon footprint to changes in this site-specific variable is investigated later in this study.

Daniel and Koerner (2007) recommend that the subgrade on which a compacted clay liner is placed should provide adequate support for compaction and be free from mass movements. For this analysis, subgrade preparation is assumed to consist of grading to meet elevations in the grading plan using a bulldozer and a grader. The compacted clay liner itself is constructed by first spreading the soil into thin (0.15- to 0.2-meter) lifts using a bulldozer. Each lift is subjected to numerous passes with a sheepsfoot roller, to knead the soil and break up clods and remold the soil into a homogeneous mass free of voids or large pores. In addition, water is added to produce a moisture content within specification requirements. The surface of the final lift is compacted and smoothed using a smooth-drum roller, to provide an adequate foundation for the geomembrane liner.

A typical compacted clay liner installation rate of 0.25 hectares per day (0.6 acres per day) was assumed. This corresponds to placement of 2,000 m3 of compacted soil per day, a reasonable expectation during periods of good weather. Once the compacted clay liner is completed, it is also covered with a 1.5-mm (60-mil) thick HDPE geomembrane, which is in turn covered by a 0.3-m (1 foot) drainage sand layer.

GEOSYNTHETIC CLAY LINERS

GCLs are factory-manufactured mats consisting of sodium bentonite clay between two geotextile layers, with a laboratory hydraulic conductivity of 5 x 10-9 cm/sec. Due to their low hydraulic conductivity, GCLs are frequently used as a substitute for compacted clay liners in many containment applications. Bonaparte et al (2002) provide field data from numerous landfill sites demonstrating that GCLs provide equivalent or superior hydraulic performance when compared to 0.6 meters of compacted clay as the lower component of composite liner systems.

Sodium bentonite is a rare clay mineral formed through the aqueous deposition and weathering of volcanic ash. Much of the worldwide sodium bentonite supply lies within the United States, in Wyoming and South Dakota. Trauger (1994) provides a detailed description of the bentonite exploration and mining process. As with the compacted clay liner option, for the purposes of this analysis, emissions associated with upfront exploration and characterization of the bentonite deposits are not being included in the analysis, as they are not expected to be a significant contributor to the overall carbon footprint. Other excluded emissions are identified later in this paper. The analysis will begin with the mining of the bentonite. The typical mining sequence involves excavation of a series of pits. Each pit is approximately one to two acres in area and 5 to 10 meter deep. The bentonite itself occurs in beds that are one to two meters thick. To extract the bentonite, topsoil and overburden are first removed using standard earthmoving equipment. The bentonite, typically gray in color, is easily distinguishable from the overburden and subsoils. As bentonite is removed from one pit, an adjacent pit is excavated. The overburden and topsoil from the adjacent pit are used to backfill the first pit, as part of a continuous reclamation process intended to minimize the disturbed area. The reclaimed pit is graded and seeded, and the mining and reclamation process continues in this fashion until the claim has been fully utilized.

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Once excavated from the pit, the “crude” bentonite is placed in haul trucks and transported a short distance to the processing plant. The bentonite mines are located a short distance from the processing plant in Lovell, Wyoming (varying from as close as 1 km up to several km). For the purposes of this analysis, a distance of 30 km was conservatively assumed.

When the bentonite arrives at the bentonite plant, it is segregated into different stockpiles based on grade. The stockpiled material is plowed to facilitate air drying, and depending on the intended end use, may also be blended with other grades of bentonite. The field-dried and blended bentonite is carried into the plant, where it is dried further in an oven. The material then is passed through a crusher to reduce the clay particle size.

The dried and crushed clay is stored in a holding tank until all bentonite quality tests (e.g., fluid loss and free swell) are completed. From there, the clay is transferred by a belt conveyor to the GCL manufacturing line. The GCL manufacturing process, shown in Figure 1, begins by applying bentonite at a typical loading rate of 4.3 kg/m2 between two geotextiles (in this example, a cover nonwoven geotextile and a base woven geotextile). The woven and nonwoven geotextile components of the GCL are purchased from an outside manufacturer, located in northern Georgia, approximately 2,760 km (1,700 miles) away. The three layers are then passed through a needlepunching loom, where fibers from the nonwoven cover geotextile are driven through the bentonite layer and into the woven base geotextile.

Figure 1. GCL manufacturing process.

The finished reinforced GCL is packaged in rolls, each containing 209 m2 of material. GCL rolls are transported to the job site using either flatbed trucks or closed vans. This study assumes that the distance from the GCL production plant in Lovell, Wyoming, to the job site is 1,610 km (1,000 miles). Each truck can hold up to 17 rolls, or 3,555 m2 of GCL. Using a waste factor of 1.15 (for overlap and scrap), it is estimated that 3.24 truckloads of GCL would be needed to line a one-hectare area.

As the trucks arrive at the job site, the GCL rolls are unloaded using an extendible boom fork lift equipped with a stinger bar. Prior to deploying the GCL, the subgrade soil is prepared to meet project specifications. Subgrade preparation before placing a GCL is typically more involved than the preparation needed prior to constructing a compacted clay liner. As with the

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compacted clay option, the existing soil surface is graded to meet the elevations in the grading plan using a bulldozer and a grader. In the case of the GCL, an additional step is necessary; a smooth-drum roller is driven over the subgrade to ensure that the finished surface is firm, smooth, and free of large stones that could puncture the liner.

Once the subgrade has been prepared, the GCL rolls are deployed using a spreader bar and core pipe, which can be suspended from common construction equipment, either a front end loader, backhoe, or excavator. A typical GCL installation rate of 0.4 hectares per day (1 acre per day) was assumed. Once deployed, the GCL is covered with a 1.5-mm (60-mil) thick HDPE geomembrane, which is in turn covered by a 0.3-m (1 foot) layer of drainage sand.

METHODOLOGY Protocol and Boundaries of Analysis

To complete a Carbon Footprint calculation, one must set the boundaries of the calculation. The boundary establishes what is included in the calculation and what is excluded from the calculation. The de facto standard in GHG reporting is the World Resources Institute (WRI) “GHG Protocol-A Corporate Accounting and Reporting Standard, Revised Edition” (WRI, 2004) (“Protocol”). This Protocol was developed to assist organizations in calculating a corporate-wide or organization-wide GHG footprint and breaks out the boundary analysis under the categories of “organizational boundaries” and “operational boundaries”. However, this paper did not focus on an “organizational” calculation, but instead, provides a comparison of the GHG emissions attributable to two different liner systems (GCL versus CCL). Because the production and installation of each of these systems involves emissions attributable to multiple organizations and processes, certain aspects of the WRI Protocol are not directly applicable or relevant. That said, some of the terminology and methodology used in this paper is consistent with and taken from the WRI Protocol.

In terms of “operational boundaries”, our calculation attempted to include all the Scope 1 (direct) emissions, the Scope 2 indirect emissions (purchased electricity), and as many of the other indirect Scope 3 emissions we could practically calculate or estimate. A more specific discussion of the emission sources included (or excluded) and the calculations are provided later in this paper. GHG Identification and CO2 Equivalents

The GHGs included in the calculation were the three (3) primary GHGs, namely carbon dioxide, methane, and nitrous oxide. Each of these gases has a different Global Warming Potential (GWP), which is a measure of how much a given mass of a greenhouse gas contributes to global warming or climate change. Carbon dioxide is by definition issued a GWP of 1.0. To quantitatively include the contributions of methane and nitrous oxide to the overall impact, the mass of the methane and nitrous oxide emissions are multiplied by their respective GWP factors and then added to the mass emissions of carbon dioxide to calculate a “carbon dioxide equivalent” mass emission. For purposes of this paper, the GWPs were taken from the values listed in the USEPA regulations “Mandatory Reporting of Greenhouse Gas Emissions” (USEPA, 2010). The GWPs for the GHGs considered in this analysis are:

Carbon Dioxide = 1.0

Methane = 21.0

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Nitrous Oxide = 310.0

Using the relative GWPs of the GHGs, the mass of carbon dioxide equivalents (CO2eq) was calculated as follows:

(1) GHG Estimates using Emission Factors and Higher Heating Values

The details and supporting references regarding the individual calculations are provided in more detail in Appendix A and Appendix B, but in general, the GHG emissions were calculated using Emission Factors (EF). In some cases where necessary, Higher Heating Values (HHVs) were also used to convert fuel-use quantities to energy, in cases where the EFs were based on energy units (and not fuel volume or mass). A GHG Emission Factor (EF) is simply a ratio of GHG emitted per unit quantity of energy consumed or material produced (depending on the specific factor). Emissions Not Considered

As mentioned previously, this paper did not focus on a comprehensive “organizational” calculation, but instead, provides a comparison of the GHG emissions attributable to two different liner systems (GCL versus CCL). While an attempt was made to reasonably include as many emission sources as possible, selected emission sources were excluded from the study boundaries, since they represent a very small percentage of the overall total carbon footprint and are difficult to estimate. Excluded sources include:

Emissions associated with the exploration/extraction/production and transport of the fuels themselves.

Emissions associated with the exploration/characterization of the clay borrow source (option 1) and bentonite pits (option 2).

Emissions associated with disposal of any wastes at the Lovell, Wyoming GCL manufacturing plant, as well as wastes generated by raw materials suppliers (e.g., geotextiles, resin).

Emissions associated with commuting/business travel of employees of the material suppliers, engineers, and contractors working on the project.

Additionally, the carbon footprint values for the layers placed over the low-permeability soil layer (the HDPE geomembrane and the 0.3-meter thick drainage sand layer) were estimated using solely the emission factors in the Inventory of Carbon and Energy (ICE) (Hammond and Jones, 2008), and do not include transport, installation, etc. This approach was considered to be reasonable, since these layers are identical for both of the liner options under consideration, and their footprints simply cancel each other out in the overall comparison.

Even if these various sources were somehow included in the analysis, they would have little impact on the GCL:CCL carbon footprint comparison, and therefore would not change the findings or conclusions of this paper.

eqCOkgONkgCHkgCOkg 2242 0.3100.21

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CARBON FOOTPRINT ANALYSIS RESULTS

Using the assumptions listed above, carbon footprint analyses (in terms of CO2 equivalents per hectare of lined area) were performed for both the compacted clay liner and GCL options. The analyses are summarized in Tables 1 and 2, with backup calculations presented in Appendix A. CO2 emission factors for the various transportation and construction components of each process were obtained from USEPA (2005a, 2005b, 2008a, 2008b, 2008c) and University of Bath (2008). Fuel consumption rates for the various construction equipment used by both options was obtained from Caterpillar (2010). Information on the greenhouse gas emissions associated with the mining and processing of bentonite clay was provided by DAI Environmental (2010), and further described in Appendix B.

A comparison of Tables 1 and 2 shows that, for a scenario where the clay borrow source is located 16 km from the job site and the GCL manufacturing plant is located 1,610 km from the job site, the compacted clay liner option would result in significantly higher (36%) emissions of CO2 equivalents per hectare of lined area. The disparity is simply due to the greater number of trucks necessary to haul soil from the borrow source to the job site (552, compared to only 3.24 truckloads of GCL per hectare). The largest single component of the overall carbon footprint for both options is transportation: 34% for the GCL and 57% for the compacted clay liner.

Table 1 – Summary of Compacted Clay Liner Carbon Footprint

Process Step kg CO2eq / ha Assumptions 1 Excavate Soil at Borrow

Source 2,656 CAT 329 Excavator, operating 40 hours/ha. Assume 24.5

Liters/hr fuel consumption, based on medium work application and medium engine load factor (CAT performance handbook).

2 Haul Clay to Job Site 93,527 Assume site is 16 km from borrow source, and 552 truckloads (each carrying 15 m3 of clay) are needed to cover 1 hectare.

3 Subgrade preparation Rough grading 1,741 CAT D6 dozer, operating 25 hours/ha. Assume 25.7 Liters/hr

diesel fuel consumption. Fine grading 1,565 CAT 160 Grader, operating 25 hours/ha. Assume 23.1

Liters/hr diesel fuel consumption. 4 Construct Clay Liner CAT D6 Bulldozer 2,786 Operating 40 hours/ha. Assume 25.7 Liters/hr diesel fuel

consumption. CAT 815 sheepsfoot

compactor 4,553 Operating 40 hours/ha. Assume 42 Liters/hr diesel fuel

consumption. CAT 815 smooth drum

compactor 4,553 Operating 40 hours/ha. Assume 42 Liters/hr diesel fuel

consumption. 10,000-gallon water

truck 1,518 Operating 40 hours/ha. Assume 14 Liters/hr diesel fuel

consumption. 5 Geomembrane 25,944 from ICE 1.6a (polyethylene) = 1.6 tonnes CO2/tonne PE 6 Cover Soil 26,004 from ICE 1.6a (sand) = 0.005 tonnes CO2/tonne sand Totals 164,847 kg CO2eq / hectare lined area

Since material transport is such a large component of the overall carbon footprint, a sensitivity analysis for this variable was also performed, as shown in Figure 2. The figure shows the linear relationship between the distance from the clay borrow source to the job site and the overall carbon footprint associated with the compacted clay liner. Curves associated with the expected GCL carbon footprint assuming distances of 100, 1610, and 3000 km from the GCL

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plant to the job site, are also overlaid onto Figure 2. A review of this figure shows that in order for the compacted clay liner option to produce a lower carbon footprint than the GCL option (assuming the GCL manufacturing plant is located 1,610 km from the job site), the clay borrow source would need to be within approximately 9 km (5.5 miles) of the job site. If the GCL plant is located 3,000 km (1,860 miles) from the job site (since there are two plants in the United States, this is realistically the longest GCL transport distance encountered), then the clay borrow source could be within approximately 14 km (8.7 miles) of the job site and still offer a lower carbon footprint. Looking at the other extreme, if the GCL plant is located very close to the job site, say 100 km (62 miles), then the clay borrow source would need to be within 2.5 km (1.6 miles) of the job site in order to produce a lower carbon footprint.

Table 2 – Summary of GCL Carbon Footprint

Process Step kg CO2eq / ha Assumptions 1 Mine Bentonite 391 Emission factor (2.71 kg CO2e / liter diesel), from EPA420-F-

05-001. Assumes 49.45 metric tons of bentonite per hectare lined area.

2 Haul to Processing Plant 280 Emission factor (2.71 kg CO2e / liter diesel), from EPA420-F-05-001.

3 In-Plant Processing 2,126 Provided by DAI (2010). Includes bentonite processing (stockpiling, blending, drying, crushing, conveying), and GCL needlepunching. Includes all plant fuel sources (electric, gas. diesel, coal, natural gas/propane) for Jan. through Nov. 2010.

4 Geotextiles woven manufacture 3,416 From ICE 1.6a (polypropylene) = 2.7 tonnes CO2/tonne PP.

Woven geotextile weight = 0.11 kg PP/m2. transport to GCL 1,454 Distance from Georgia to Lovell, WY = 2,760 km, with 160-

km origination and return trips. 150,580 m2/truck nonwoven manufacture 6,210 From ICE 1.6a (polypropylene) = 2.7 tonnes CO2/tonne PP.

Nonwoven geotextile weight = 0.2 kg PP/m2. transport to GCL 5,269 Distance from Georgia to Lovell, WY = 2,760 km, with 160-

km origination and return trips. 28,100 m2/truck 5 Transport GCL to Job Site 41,894 Assume site is 1,610 km away, with 160-km origination and

return trips. 6 Unload GCL 949 CAT TL355 Telehandler, operating 25 hours/ha. Assume 14

Liters/hr diesel fuel consumption, based on medium work application and medium engine load factor (CAT performance handbook).

7 Subgrade preparation Rough grading 1,741 CAT D6 dozer, operating 25 hours/ha. Assume 25.7 Liters/hr

diesel fuel consumption. Fine grading 1,565 CAT 160 Grader, operating 25 hours/ha. Assume 23.1

Liters/hr diesel fuel consumption. Rolling 2,846 CAT 815 Compactor (smooth drum), operating 25 hours/ha.

Assume 42 Liters/hr diesel fuel consumption. 8 Deploy GCL 1,660 CAT 329 Excavator, operating 25 hours/ha. Assume 24.5

Liters/hr diesel fuel consumption. 9 Geomembrane 25,944 from ICE 1.6a (polyethylene) = 1.6 tonnes CO2/tonne PE 10 Cover Soil 26,004 from ICE 1.6a (sand) = 0.005 tonnes CO2/tonne sand Totals 121,749 kg CO2eq / hectare lined area

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0

100,000

200,000

300,000

0 5 10 15 20 25

Distance to Clay Borrow Source (km)

Emis

sion

s (k

g C

O 2

equi

vale

nts

/ hec

tare

) Compacted ClayGCL (100 km)GCL (1610 km)GCL (3000 km)

Figure 2. CO2 equivalent emissions as a function of distance to job site.

Not surprisingly, these relationships mimic past analyses comparing the cost effectiveness of these types of low-permeability liners. In general, the overall cost of a compacted clay liner has proven to be less than a GCL if a good quality clay source is available on-site. If soil must be brought from an off-site borrow source, the economics often tip in favor of the geosynthetic option.

SUMMARY AND CONCLUSIONS

CETCO and DAI Environmental performed an analysis comparing the carbon footprint of a conventional compacted clay liner to a GCL for a hypothetical RCRA Subtitle D municipal solid waste landfill. The analysis found that, for a landfill liner site located 1,610 km from the GCL manufacturing plant and 16 km from the clay borrow source, a conventional compacted clay liner is expected to produce a 34% larger carbon footprint than a GCL. The largest single component of the overall carbon footprint for both options is transportation. Repeating the analysis over ranges of different haul distances found that in order for the compacted clay liner option to produce a lower carbon footprint than the GCL option, the clay borrow source would need to be within approximately 9 km (5.5 miles) of the job site. This assumes that the GCL manufacturing plant is located 1,610 km from the job site. If the GCL plant is located 3,000 km (1,860 miles) from the job site, then the clay borrow source could be within approximately 14 km (8.7 miles) of the job site and still offer a lower carbon footprint. If the GCL plant is located 100 km (62 miles) from the job site, then the clay borrow source would need to be within 2.5 km (1.6 miles) of the job site to produce a lower carbon footprint.

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As is the case with evaluations of cost effectiveness, carbon footprint evaluations are site-specific, depending greatly on the relative distances of the project site to the clay borrow source and to the GCL manufacturing plant. Accordingly, the conclusions of this study should not be applied to every site; project-specific analyses are strongly recommended.

REFERENCES

1. Bonaparte, R., Daniel, D. E. and Koerner, R. M. (2002), “Assessment and Recommendations for Optimal Performance of Waste Containment Systems”, EPA/600/R-02/099.

2. Caterpillar Performance Handbook, Edition 40, January 2010.

3. DAI Environmental, Inc. (2010), AMCOL Greenhouse Gas Emissions, Internal Report.

4. Daniel, D.E. and R.M. Koerner (2007), Waste Containment Facilities: Guidance for Construction Quality Assurance and Construction Quality Control of Liner and Cover Systems.

5. Hammond, G. and C. Jones (2008), “Inventory of Carbon and Energy (ICE), Version 1.6a”.

6. Trauger, R.J. (1994), "The Structure, Properties, and Analysis of Bentonite in Geosynthetic Clay Liners," Proceedings of the 8th GRI Conference: Geosynthetic Resins, Formulations, and Manufacturing, Geosynthetic Research Institute, Drexel University, Philadelphia, PA, pp. 185-198.

7. USEPA (2005a), “Emission Facts: Average Carbon Dioxide Emissions Resulting from Gasoline and Diesel Fuel”. Office of Transportation and Air Quality, EPA-420-F-05-001.

8. USEPA (2005b), “Emission Facts: Metrics for Expressing Greenhouse Gas Emissions: Carbon Equivalents and Carbon Dioxide Equivalents”. Office of Transportation and Air Quality, EPA-420-F-05-002.

9. USEPA (2008a), “eGRID-The Emissions and Generation Resource Integrated Database for 2007”. USEPA Agency Office of Atmospheric Programs.

10. USEPA (2008b), “Climate Leaders Guidance for Direct Emissions from Mobile Combustion Sources”. Office of Air and Radiation (6202J), EPA430-K-03-005.

11. USEPA (2008c), “Climate Leaders Guidance for Optional Emissions from Commuting, Business Travel, and Product Transport”. Office of Air and Radiation (6202J), EPA-430-R-08-006.

12. USEPA (2010), “Mandatory Reporting of Greenhouse Gas Emissions”, Code of Federal Regulations, Title 40, Part 98.

13. WRI (2004), “GHG Protocol-A Corporate Accounting and Reporting Standard, Revised Edition”. World Resources Institute.

14. WRAP (2009), “Sustainable Geosystems in Civil Engineering Applications”.

APPENDIX ACALCULATION OF CO2 EQUIVALENTS FOR CCL AND GCL OPTIONS

EFyzo: N2O emission factor (0.0027 g Nzo/ton-A. COMPAP,TED CLAY LINERGiven:r 0.6-meter thick compacted soil liner

. Clay density: 1400 kg/m3 (loose)

o Compaction factor : 1.38

. Compacted soil liner can be placed at a rate of1500 m3/day. 4 days to line a one-he ctate area(10 hours/day).

. Fuel consumption rates based on medium workapplication and medium engine load factor

o Emission Factors, from EPA 430-K-08-004 andEPA 430-R-08-006:

10.15 kg CO, x tal _ 2.68 kg CO,

gal diesel 3.785 L L diesel

0.26 g N,O , gal ,0.31

kg CO, eq

gal diesel 3.785L INrO

ton - mile totrne l.6l km tonne- km

6 = 77i7 *0'204 kg CO'eq

tonne - km

Where:E -Total CO2 equivalent emissions (ftg)TKZ : Tonne-kilometers Traveled

A1. Excavation at Borrow SourceAssumptions:

. A CAT 329 Excavator is used, operating 40

hours/hectare. The diesel fuel consumption rate

is 24.5 Liters,4t (CAT).

40 hours 24.5 L diesel ,2.71

kg COreq _2656 kg COreq

hectare hour L diesel hectare

A2. Transport to Project SiteAssumptions:o Distance from Borrow source to Job Site

(Hypothetical): 16 km

. Empty (Tare) Truck Weight: 15455 kg

truck

. T)pical T,oad of Soil :l5mt .14ookg 2loo0lgIrrrk *' - ,rrrk

r T)pical Loaded Truck Weight (Soil) :21000 kg , 1s455 kg _36455 kg

truck truck truck

Loaded Trucks (16-km trip from Borrow Source toJob Site):

mile)Converling to Metric Units:

0.298 kg CO, ,7.702

tons , mile _ 0.204 kg CO,

8280m3 looseclay

hectare

1.44gCHo* gal ,gal diesel 3.785 L

0.02I kg CO, eq

9CH^

0.021kg CO, eq

L diesel

_0.008 kg CO, eq

L diesel

. -7 Liter diesel = 2.68 + 0.02I+ 0.008 = 2.71 kg COreq

r Emission Factor for HDPE geomembrane, from

ICE (2008): l'6 tonnes CO.

tonne HDPE

Emission Factor for sand, from ICE (2008):0.005 tonnes CO,

tonne sand

On-Road Truck Product Transport Emissions:

E = TMT, \EFr,o,+ 0.021 . EFr,,, +0.3 1 0. EFrl,o)

E = rMr x (o.zsi +(o.oz I o.oo:s)+ ( o.s to. o.oozt)) = ru, " \f#J

Where:E:Total CO2 equivalent emissions (ftg)TMT: Ton Miles TraveledEFco:: CO2 emission factor (0.297 kg COy'ton-mile)EF cru : CHa emission factor (0.003 5 g CHq/ton-mile)

o.u * "ffi x I 3 8 (c ompact i on fact or) =

8280 m3 loose clav truck 552 trucks

hectare 15 m3 hectare

u =(ru mrruott kt , tonne ,552 rrucks\^o.zoq ts cOr"q -65682

kg Coreq

( truck 1000 kg hecrue ) bnne-km hectdre

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EmptyTrucks(16-kmreturntriptoBonowSource): r A CAT 815 Compactor (smooth drumroller) is

used for compaction of final surface prior toU,( ,o^r. 154554g ronnc .552irac&sl^ o.2o4kgCO_eq .2'784oApCO.eq

| *uck l000isr hectare ) tonne-km ffi geomernbrane installation, operating 40

, . ; hours/hectare. The diesel fuel consumption rate

is 42 Liters/hr (CAT).Total:

, _ 65682 kg CO,eq *27846 kg COreq _93528 kS CO.eq 40 hours ,42 L diesel ,2.71 kg CO,eq _ 4553 kg CO,eq

"(( t hectare hectare hectare hectare hour L diesel hectare

A3. Subgrade PreparationAssumptions: o A 10,000-gal water huck is used for clay

morsfure conditioning, operating 40

. All fill volumes needed to meet grading plan are hours/hectare. The diesel fuel consumption rate

available on-site. is 14 Liters/hr'

40 hour.g ,14 L diesel ,2.71k9 COreq _1518 kg Coreqo A CAT D6 Bulldozer is used for rough grading, -operating 25 hours/hectare. The di.r.i-#i hectare hour L diesel hectare

consumption rate is 25.'7 Liters/hr (CAT).A5. Geomembrane

25 hours *25.7 L diesel ,2.71kg COreq __1741 kg COreq Assumptions:hectare hour L diesel hectare

r 1.5-mm thick HDPE geomembrane, with density:940kghi.

o A CAT 160 Motor Grader is used for finegrading, operating 25 hours/hectare. The diesel o HDPE carbon footprint is 1.6 kg CO2 I kgtuel consumption rate is 23.1 Liters/hr (CAT). polyethylene (ICE, 2008).

25 hours 23.1 L diesel 2.7 l kg Co-eq 1565 kg Coreq 1olg ^^",. 10000rrr , 16215 ks HDpE

hectare' no* "- tffi' =--nior"'' -;'uuul)'/' h"r*r,'ll)(rcrap)- t"rrr"

16215 kg HDPE "1.6

kg CO. ,25944 kg CO.eq

A4. Compacted Clay Liner Construction hect^re kg HDPE hectare

r A CAT D6 Bulldozer is used for spreading soil, A6. Sand Cover Soil

operating 40 hours/hectare. The diesel fuel Assumptions:

consumptionrateis25'l Liters/hr(cAT)' o 0.3-meter thick drainage sand layer, with in-

40 hours 25.7 L diesel ,2.71kg COreq _2786kg COreq place density :1733 kg/m3.

hectare hour L diesel hectareo Sand carbon footprint is 0.005 kg CO2 / kg sand

(rcE,2008).

r A CAT 815 Compactor (sheepsfoot roller) is

used during construction of each lift, operatin, 1733ks "0.3r"

19000t' -5'2x106

kg sand

40 hours/hectare. The diesel fuel consumptioi rn' hectare hectare

rate ts 42 Liters/hr (cAT)' 5.2x106 kg sand * 0.005 kg co, _26000 kg coreq

40 hours 42 L diesel 2.71kg Coreq 4553 kg coreq hectare kg sand hectare

hectare hour L diesel hectare

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B. GEOSYNTHETIC CLAY LINERGiven:. The GCL is manufactured wilh4.3 kg/m2

(typical) bentonite placed between a 200 g/m2nonwovein'cover geotextile and, a 105 g/m2woven base geotextile.

2.5 days to line a one-hectare area (10 hours/day)

Emission Factor for polypropylene geotextiles,

lrom ICE (2008): 2 7 ronnes Co,tonne polypropylene

Emission Factor for bentonite processing atLovell, Wyoming plant (DAI,2010):

43 kg COreq

tonne bentonite

81. Bentonite Mining

4.3 ke benronire 10000 rr tonne--_-:-- .l.l>lscraDl_

n hecrare I 000 kg

Distance from Geotextile Plant (Ringgold, GA)to GCL Plant (Lovell, Wyoming) - 2760 km

Nonwoven Geotextile Load -28100 m) . 0.2 kg ,5620 kg

trrrk ^ nf --trucl<

Loaded Truck Weight (Nonwoven Geotextile) -5620 ks

*15455 kg _21075 ks

truck truck lruck

Loaded Truck (from Geotextile Plant to GCL Plant):

1 0000 rz )

. '1.15 \suop)-hectare

t _( ZtoO *,n . 21015 kg toilne 0 40j //4( *s I .0.204 kg CO,eq _ 4853 kg CO,eq

[ 1/rck I 000 lg hectare ) ronne - km hecrare

Emptlz Truck (Originates 160 km from GeotextilePlant. and Continues to next destinatiorl within 160km of GCL Plant):

t _( l,ro t,, . t5455 kg tonile 0l09gtr I .

0.204 kg CO,eq _ 20o kg CO,eq

\ truck I 000 kg hecrare ) tonne - km hecrare

Total:

r 4853 kg CO,eq , .L\onrnr.n--r-he(lare

( zoo *g co,eq\ 5265 kg co,eq

I t*r,*" )- t*r**

Manufacturing (Woven)

0.1 I fe 10000rr' ronne l.265ronnes PP' 1. l: ls(/aD I -m hectore I 000 ,(g hecrare

1.265 tonnes PP 2.7 tonnes CO. 1000 kg 3416 kg CO.

-x

0.409 truckloacls NI(

0.1 sol .3.185 L ton .24bt .1000,(g _ 2of!_!,r:!lton gdl 2000 lbs kg tonne tonne bentonite

49.15 tonnes bentonite , 2.91 L diesel ,2.71kg CO.eq _391 kg CO.eq

tonne bentonite L cliesel hectare

82. Bentonite Transport to Plant

O.5 gal .3.785 L ton 2.2 lbs 1000 kg 2.08 L diesel

ton gdl 2000 lbs kg tonne tonne bentonite

49.45 tonnes bentonite , 2.08 L diesel *2.71

kg CO,eq _280 kg CO,eq

tonne bentonite L tliesel hectare

83. Bentonite ProcessingA{eedlepunching at

Lovell, Wyoming plant

43 kg COreq ..49.45 tonnes 2126 kg CO,eq

tonne bentonite hectare hectare

84. GeotextilesManufacturing (Nonwoven)

0.2 ks 10000 rn2 tonne 2.3 tonnes PP---::x > l.l5{scrap}=m' hecrare I 000 ig hectare

2.3 tonnes PP 2.'l tonnes CO, . 1000 kg 6210 kg CO.

hectare tonne PP tonne hectare

Transport to GCL Plant (Nonwoven)Assumptions:

tonne PP tonne hectarr:

Transport to GCL Plant (Woven)Assumptions:r Distance from Geotextile Plant (Ringgold, GA)

to GCL Plant (Lovell, Wyomrng) :2760 km

. Woven Geotextile Load:150580rr2 0.1 I /rg 16564kg

rurk^ri=trrrk. Loaded Truck Weight (Woven Geotextile) -

16564 kg I 5455 kg _320t9 kg

truck truck truck

49.45 torutes bentonite

28100 m NlY geotextile

hectare

tuck150580 z'? I;t/ geotextile

l0000n: 0.0Totruckloaclslt.1.15(sc/ap)hecltttc hcctdrc

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Loaded Truck (from Geotextile Plant to GCL Plant):

, =( rrno f- ^rt!le kg

^ ronne

^ 0.0?tr ira.{r)^ 6.204 kg COreq _ 1370 Ag CO,eq

I truck 1000 4g hecture ) ronne- km hecture

'..;

Empty Truck (Originates 160 km from geotextileplant. and continues to next destination within 160km of GCL Plant):

t . (rc0 m. 15455 g . :l!l: 0.01o trucks)^0.204 ks CO,eq 38 kg CO,c,1

\ truk l000tg hecr,tre ) ronnc -Am herure

Total:, _ ll70 ks CO,eq

" (38 Ag CO.eq \ 1446 kg CO,eq-"--- h"rt*, --l t*"** )- ho*,u

85. GCL Transport to Job SiteAssumptions:o Distance from GCL Plant (Lovell, Wyoming) to

Job Site (Hypothetical): 1610 km

Empty (Tare) Truck Weight = 15455 kg

86. Unloading GCL RollsAssumptions:

. A CAT TL355 Telehandler is used, operating 25

hours/hectare. The diesel fuel consumption rate

is 14 Liters/hr (CAT).

25 hours l4 L diesel 2.71Ag CO.eq 949 kg CO.eq

hectare hour L diesel hectare

B7. Subgrade PreparationAssurnptions:

. All fill volumes needed to meet grading plan isavailable on-site. Subgrade rough grading

estimates same as with compacted clay lineroption (see A3 above).

A CAT 815 Compactor (smooth drum roller) is

used for final subgrade rolling prior to placement

of the GCL, operating 25 hours/hectare. The

diesel fuel consumption rate is 42 Literslfu(cAr).

25 hours *42 L diesel *2.71k9 COreq _2846 kg COreq

hectare hour L diesel hectare

88. Deploying GCL RollsAssumptions:

o A CAT 329 Excavator is used, operating 25

hours/hectare. The diesel fuel consumption rate

ls 24.5 Liters/hr (CAT).

25 hours 24.5 L diesel 2.71, kg CO.eq 1660 kg CO"eq

hectcLre hour L diesel hectare

truck

. T)pical GCL Load: 20910 kg

truck

. Tlpical Loaded Truck Weight (GCL) :20910 kg , 15455 kg _36365 kg

truck truck truck

Loaded Truck (from GCL Plant to Job Site):

10000 n' GCL roll rruck r I.15(scrorl_hecrare 209 m' 17 rolls GCL

3.24 truckloacls GCL

t =( lolo *,n .36364 ks ronne ,3.24 rrucks 1.0.204

kg CO,eq _38697 Ag CO.eq

\ trucl 1000 lg hecrore ) ronne kn hecrare

Empty Truck (Originates 160 km from GCL plant.and continues to next destination within 16Q km ofJob Site):

- ( , , ^ , 15455 kg ronne 3.24 trucks\ 0.204 ke CO.eq lh34 Ag e O.eq.-\ rruck I 000 lg hecrare ) tontte - kn het rare

Total:F _ 386s7 kg Coreq . (tott *g CO.eq \ 4teb6 kB CoreqL'tL=

h"* " t l h"rr"* )- h"rr*

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APPENDIX BEMISSIONS FROM BENTONITE PROCESSING

As part of AMCOL's corporate GHG strategy, each facility measures and reports all of the major components oftheir energy ude'at each facility. This information was used to calculate the GHG emissions for the Lovell plant.The processes at the plant assumed to be incorporated into the energy use reported by the plant included stockpiling,blending, drying, crushing, conveying, and GCL (needlepunching) processes. The plant fuel and energy useincluded in the analysis were purchased electricity, gasoline and diesel fuel consumed at the plant, and coal, naturalgas, and propane burrred at the plant. The data provided and incorporated in the analysis covered the time periodfrom January l, 2010 to November 30, 2010. Over this time period, AMCOL also reporled the total tons ofbentonite processed at plant. The GHG emissions in units of kg CO2-equivalents (COreq) were calculated, and thisvalue, along with the reported weight of bentonite processed at the plant over this same time period, was used tocalculate a "in-plant processing" CO2eq emission factor in units of kg CO2eq/tonne bentonite processed.

Scope 1-Direct EmissionsUsing the WRI Protocol definitions, Scope 1 Direct Emissions at the plant included emissions from the on-siteand/or in-plant burning of nafural gas, propane, coal, diesel fuel, and gasoline.

Natural Gas: The plant natural gas consumption data was given in energy units of mmBTU, and then for purposesof this paper, converted into S.I. units (gigajoules, or GJ). The GHG emissions in terms of CO2eq associated withnatural gas were calculated using emission factors for "pipeline natural gas" and Global Warming Potentials(GWPs) fromUSEPA 40 CFR 98 (2009).

Where:E -Tota7 CO2 equivalent emissions (ftg)GJ--Energy Value of Natural Gas Burned from 1/1/10 - lll30l10 (GJ)GIryPco2: I kg CO2eq/kg CO2

GWP1H4: 2I kg CO2eq/kg CHa

GI(P926: 310 kg COzeq/kg N2O

EFcoz: CO2 emission factor (50.26 kg CO2/GJ), (53.02 kg CO2/mmBTL,\EFcru- CHa emission factor (0.0009479 g CHy'GJ), (0.001 ftg CHy'mmBTQEFw:o: N2O emission factor (0.00009479 g N2O/GJ), (0.0001 kg N2O/wwBTQ

Propane: The plant propane gas consumption data was given in units of gallons, and then, for purposes of thispaper, converted into SI units (liters). To determine the GHG emissions in terms of CO2eq associated with thepropane combustion, the Higher Heating Value (HHV), emission factors, and Global Warming Potentials (GWPs)from USEPA 40 CFR 98 (2009) were used.

Where:E:Total CO2 equivalent emrssions (kg)Z: Volume of Propane burned from 1/1/10 - 11130110 (liters)HHV : Higher Heating Value of Propane (0.0254 GJ/liter)GWPco2: I kg CO2eq/kg CO2

GWPctu: 2l kg CO2eq/kg CHa

GWP1126: 310 kg CO2eq/kg NzOEFcoz- CO2 emission factor (61.10 kg CO2/GJ), (61.46 kg COy'mmBTAEFcat - CHa emission factor (0.0028a kg CHy'GJ), (0.003 kg CHa/mmBTQEFnzo: N2O emission factor (0.000569 kg N2O/G4, (0.0006 kg N2O/mmBTL)

Coal: The plant coal cornbustion data was given in units of U.S. (short) Tons, and then, for pulposes of this paper,

converled into SI units (tonnes). The plant also reported that the coal combusted at the plant was sub-bituminous

E=GJ*(""'or'"'or+ GWP*H4 uo'oo+ GWP*'' uo*p)

E =v x HHV r(ororor.uoror+ GWPrro ,oruo+ GIIP*ro rr*ro)

-155-

coal. To determine the GHG emissions from plant coal combustion, the Higher Heating Value (HHV) and emissionfactors for sub-bituminous coal from USEPA 40 CFR 98 (2010) were used. To convert the individual GHGemissions into CO2eq, Global Warrning Potentials from USEPA 40 CFR 98 (2010) were used.

,(\E:W v HHy x lj*rro, "ror+

Gtilprro. EFcHq+ GWpN20. e rrro )

Where:E - Total CO2 equivalent emissions (frg)

W:Weight of Coal burned from 1/1/10 - 11130110 (tonnes)HHV: Higher Heating Value of Coal(20.06 GJ/tonne)GI4/Pco2: I kg CO2eq/kg COzGWP1H4: 2l kg CO2eq/kg CHaGWP7127: 310 kg CO2eq/kg N2OEFco: - CO2 emission factor (91.96 kg CO2/GJ), (91.02 kg COy'mmBTt\EFc*: CHa emission factor (0.010a kg CH/GJ), (0.011 kg CHy'mmBTL\EFxzo: N2O emission factor (0.00152 kg N2O/GJ), (0.0016 kg N2O/wwBTU)

Diesel Fuel: The plant diesel fuel consumption data was given in units of gallons, then for purposes of this paper,converted into liters. To deterrnine the GHG emissions from diesel fuel combustion, emission factors taken from theUSEPA "Mobile Source" guide (EPA430-K-08-004) (2008) and Global Warming Potentials from USEPA 40 CFR98 (20 10) were used. Because the plant did not provide a detailed breakout as to the volume of diesel fuel used foreach type of piece of equipment or vehicle, a reasonable assumption of "construction equipment" for thevehicle/equipment tlpe was made.

Where:E: Total CO2 equivalent emissions (ftg)Z: Volume of Diesel fuel burned from 1/1/10 - lll30l10 (liters)GWPco2: I kS CO2eq/kg COzGWP1H4: 2l kg CO2eq/kg CHaGWPN27 : 310 kg CO2eq/kg N2OEFco:: CO2 emission factor (2.68 kg COy'liter), (10.15 kg COy'gailon)EFc*: CHa emission factor (0.000153 kg CHy'liter), (0.00058 kg CHa/gallon)EFyzo: N2O emission factor (0.0000687 kg N2O/liter), (0.00026 kg N2O/gallon)

Gasoline: The plant gasoline fuel consumption data was given in units of gallons, then for purposes of this paper,converted into liters. To determine the GHG emissions from gasoline fuel combustion, emission factors taken fromthe USEPA "Mobile Source" guide (EPA430-K-08-004) (2008) and Global Warrning Potentials from USEPA 40CFR 98 (2010) were used. Because the plant did not provide a detailed breakout as to the volume of gasoline fuelused for each tlpe of piece of equipment or vehicle, a reasonable assumption of "construction equipment" for thevehicle/equipment tlpe was made. The gasoline fuel carbon dioxide and nitrous oxide emission factors listed in theguidance are independent of vehicle type. However, the methane emission factors vary by vehicle t1pe, and as such,an assumption on "vehicle type" had to be made.

Where:E --Total CO2 equivalent emrssions (ftg)Z: Volume of Gasoline fuel bumed from 1/1/10 - lll30ll0 (liters)GWPcoz: 1 kg CO2eq/kg CO2GY[/P1H4: 2l kg CO2eq/kg CHaGItrPN2o : 310 kg CO2eq/kg N2OEFco:: CO2 emission factot (2.33 kg COy'liter), (8.81 tg COy'gallon)EFcw: CHa emission factor (0.000132 kg CHy'liter), (0.00050 kg CHa/gallon)

E =v x (orrror. uoror+ GWproo. EFcHq+ Glttp*ro **ro)

E = v x (rrrror. uoror+ GWproo. EFcHt* GWpuro **.o)

-156-

EFr,rzo: N2O emission'factor (0.0000581 kg N2O/liter), (0.00022 kg N2O/gallon)

Scope 2-Indirect Emissions from Purchased ElectricitvThe facility provided their purchased electricity quantity in units of kilowatt-hours, which, for purposes of thecalculations ware converled into megawatt-hours (MWH). To estimate the associated GHG emissions for thispurchased electricity, emissions factors for the region that facility is located in were obtained from the USEPA"eGRID 2007-version 1.0" (2008). To convert the individual GHG emissions into CO2eq, Global WarmrngPotentials from USEPA 40 CFR 98 (2010) were used. The facility is located in eGRID Region "WECCNorthwest", which carries the Region Code "NWPP".

E = MWH , ("*oror. ,rro, + Gltpruo. EFcHc + GWp*ro)

EFr,o I

Where:E:Total CO2 equivalent emissions (kg)MWH - Energy value (Megawatt-Hours) of Electricity purchased fromlllll0 - lll30ll0 (MWH)Gll/Pco2: 1 kS CO2eq/kg CO2GWP1H4: 2l kg CO2eq/kg CHaGWPN27: 310 kg CO2eq/kg N2OEFco: - CO2 emission factor (409.26 kg CO2/MI4I{1, (902.24 lbs COr/MIltH)EFcru: CHa emission factor (0.0088 kg CHy'MWHL (0.0193 lbs CHy'MITII)EFyzo: N2O emission factor (0.0068 kg N2O/MWII), (0.0149 lbs N2O/MWII)

Summary of Plant Processing Emissions and Factor CalculationFigure B-l summarizes the calculated plant processing emissions by providing the relative percentages of the totalplant emissions by GHG source.

Plant GHG Emissions

ffi Electricity

s Naturrl Gas

riiii DiBssl

H Coal

"m Gaxotine

Vil, ?ropane

Figure B-1. Relative Plant CO2 Equivalent Emissions Broken Out by GHG Emission Source

The total CO2eq value for the plant was used to calculate an "in-plant processing" emission factor, scaled to thetorures ofbentonite processed in the plant:

E kg CO, eq 43.00 kg CO, eq

T tonnes bentonite tonnebentoniteWhere:E --Total CO2 equivalent emissions from l/1/10 - lu30ll0 (kg)T - Total bentonite processed by the plant from 1/1/10 - 11130110 (tonnes)

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‐158‐  

GEOMEMBRANES: FUNCTION AND DESIGN INTO SUSTAINABLE SYSTEMS AND BEYOND

Paul E Oliveira, Technical/R&D Manager Firestone Specialty Products Company, Indianapolis, IN USA

ABSTRACT

When one thinks about how to design sustainable water management systems, one thing they must consider how to manage conditions like storm water causing erosion. It is at this point that geomembrane liners become a critical factor in the elements of design and function. Geomembranes are, by their nature, capable of stopping the impact of water flow through containment and detainment, as well as redirection. This is all accomplished by using a thin, flexible, conformable factory produced liner that, once installed, has little or no impact on the visual aspects of the design. The purpose of this presentation is to explore the various ways that geomembrane liners can be incorporated into sustainable green technologies, renewable energy, water harvesting, irrigation and storm water management designs and how they assist in making these systems work. From the simple rain garden to the highly engineered, multifunctional filtering and collection systems being done today, geomembranes are being used in projects ranging from 100 square feet to millions of square feet and are continuing to challenge the imaginations of designers and engineers around the world.

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REDUCED CO2 EMISSIONS AND ENERGY CONSUMPTION WITH GEOSYNTHETIC INSTALLATIONS Boyd J. Ramsey GSE Lining Technology LLC., Houston, TX USA Chris Eichelberger American Environmental Group Ltd., Richfield, OH USA ABSTRACT In April of 2010, GSE released a technical note entitled: Geosynthetics lower CO2 emissions and energy consumption vs. traditional soils based construction techniques. This document compared the environmental impact and energy consumption of a hypothetical geosynthetic installation with that of an installation using traditional soil (clay and stone) design and construction techniques. This analysis contained a great many assumptions that have already been improved upon with time. The other presenters and papers in this conference have completed a more detailed and exacting analysis for similar situations and topics. While I was satisfied with the original analysis and stand by the conclusions stated therein, I wanted to improve the detail and accuracy of the analysis; particularly in the area of the energy consumption and CO2 emission related to the construction and installation process of the geosynthetic layers. I believe that our industry should have as thorough knowledge as possible of the installation portion of the topic that is directly related to geosynthetic materials. The data and information presented in this paper is a summary of the energy (fuel) consumption and the resulting CO2 emissions for a geosynthetic installation in northeastern Texas. The site is a liquid impoundment with a footprint of approximately 15,000 square meters (~ 3.8 acres) and a maximum depth of 13 meters (~45 feet). The installation includes a geosynthetic leak detection layer and a geomembrane barrier. A summary of the machinery used, fuel consumption, and the resulting CO2 emissions levels are included. BACKGROUND This installation is the re-lining of a site which previously had a geomembrane barrier. The existing geomembrane barrier was aging and it was decided to install a new geosynthetic system over the existing geomembrane barrier which was not removed. Figure 1 below illustrates the cross-section of the new double geomembrane lined systems (with intermediate geonet) placed immediately over the existing geomembrane.

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Figure 1. Cross section of installed system over existing geomembrane .

Table 1 presents a summary of the equipment used on site and the daily fuel

consumption. Two key factors were identified that would have a significant impact of fuel usage. Most important is the location of the material staging area relative to the site. Transportation of roll goods at this point is one or two rolls at a time and is usually done with a front-end loader or other relatively low “mileage” equipment. At a location where the distance between the staging area and the deployment site is large (distances of approximately a kilometer (~ 1000 yards)) are not uncommon and cause a significant increase in fuel consumption. Also, at more remote sites, available lodging for the installation crews can be located 80 kilometers (~ 50 miles) or more from the site, resulting in long daily commutes. That said, neither of these latter situations occurred at this site.

Table 1 – Equipment and fuel consumption list. Fuel consumption listed is for a full day of

operations (equipment 100% utilized, approximately a 10 hour working day)

Equipment description

Daily fuel consumption in Liters/Day (Gallons/Day)

Ford F-350 diesel pickup truck 40 liters (10 gallons) Ford F-350 diesel pickup truck 40 liters (10 gallons) Ford E-350 diesel passenger van 8 liters (2 gallons) Bobcat T-250 Posi-track 75 liters (20 gallons) Deere 544-J front end loader 151 liters (40 gallons) Deere 200CC excavator 227 liters (60 gallons) Kubota GL7000 diesel generator (4) 17 liters (4.5 gallons) each Kubota GL6500 diesel generator 17 liters (4.5 gallons)

This equipment was used by a crew of ten (10) installation workers with one supervisor for a total staff of 11 people. Installation began in late November and concluded just prior to the Christmas holidays. The team was on site for 22 days. The total installed area (all layers) was ~ 46,000 square meters (~11.4 acres). This fairly slow installation pace was the result of several unique installation details, (i) the installation of two drainage (leak detection) channels running the length of the site and (ii) the adjoining sumps and the installation crew being responsible for all aspects of the anchor trench surrounding the peak of the slopes. This time duration also includes full leak detection surveys of both the secondary and primary geomembrane layers.

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During this installation process, fuel usage was a total of 3,255 liters (860 gallons). This results in CO2 emissions of 8,560 kg. The fuel usage compares to an estimate of 190 liters (50 gallons)/acre fuel consumption that was used in the initial calculations for the technical note mentioned above. With an installed area of ~ 46,000 square meters (~11.4 acres), using the estimates made in the technical note, the expected fuel usage was ~ 2,160 liters of fuel (570 gallons). CONCLUSIONS Actual fuel usage (and resulting CO2 emissions) for the installation portion of this “real-world” project was 50% higher than predicted in the original estimation. Based on this analysis, we would propose a figure of 300 liters (80 gallons) of fuel consumed per acre of geosynthetic installed. However, the contribution of the geosynthetic installation was estimated to be less than 2% of the total energy consumption and CO2 emissions for the entire project. ACKNOWLEDGEMENTS The authors would like to acknowledge Earl Morris, Jon Edens and Ron Zunker of American Environmental Group (AEG) for their valuable contributions and assistance. BIBLIOGRAPHY

1. Davis, Stacy C. et.al. Transportation Energy Data Book. (Edition 28 of ORNL-5198). US

Department of Energy. 2009. Print. (http://www-cta.ornl.gov/data/tedb28/Edition28_Full_Doc.pdf )

2. Goleman, Daniel. Ecological Intelligence: How knowing the hidden impacts of what we buy

can change everything. New York: Broadway Books, 2009. Print. 3. Hammond, Geoff and Jones, Craig. “Inventory of Carbon and Energy (ICE)”.N.p., 2 April,

2010. Web. ( http://www.bath.ac.uk/mech-eng/sert/embodied/ )

4. Heerten, Georg. “Reduction Of Climate-Damaging Gases In Geotechnical Engineering By

Use Of Geosynthetics” The International Symposium on Geotechnical Engineering, Ground Improvement, and Geosynthetics for Sustainable Mitigation and Adaptation to Climate Change including Global Warming. (2009): Print (http://www.naue.com/content-Ma/admin/img/pool/20100112103548.pdf )

5. “Calculation Tools”. The Greenhouse Gas Protocol Initiative April 6, 2010, Web.

( http://www.ghgprotocol.org/calculation-tools ) 6. “Forschungsstelle fǖr Energiewirtschaft E.V.” Research Centre for Energy Economics. April

5, 2010, Web. ( http://www.ffe.de )

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7. “Sustainableengineering.com”. Stagnito Media. March 22, 2010, Web. ( http://www.sustainableengineering.com )

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A TRUE GREEN CLOSURE; A SUSTAINABLE AND RELIABLE APPROACH USING STRUCTURED MEMBRANE AND SYNTHETIC TURF Michael R. Ayers ClosureTurf LLC Alpharetta, Georgia USA Jose L. Urrutia Riley, Park, Hayden and Associates, Inc. Duluth, Georgia USA ABSTRACT

As a response to numerous failures and poor performance of environmental closures at landfills, engineers have looked at new approaches in establishing a more physically stable and environmentally sound solution. Traditional landfills require large amounts of soil for their construction, and many experience on-going erosion and sedimentation issues. Traditional covers are highly reliant on trucking soils, heavy civil construction and on-going maintenance and repairs in order to maintain their integrity. New methods are needed to lower the impact on the environment throughout the landfill capping construction process.

A potential solution to landfill closure failures and construction and operation

environmental impacts has been the implementation of exposed geomembranes. However there are disadvantages to these systems such as: accessibility, lack of membrane protection, wind uplift issues and aesthetics. The latest approach presented here builds off of the success of using exposed geomembranes with a number of improvements to address the disadvantages of exposed systems. This system incorporates high interface friction materials, and multiple layers of protection provided by a turf system. The system is ballasted with sand infill to provide wind resistance and accessibility. Like other exposed geomembrane caps there is no soil and vegetative layer. This system also provides for a stable and rapid installation which allows for the capture of landfill gas emissions at earlier phases of development. INTRODUCTION

Sustainability for landfill closures has a dual meaning. One meaning relates to the physical stability and long-term performance and maintenance, which is a problem that has long-plagued the landfill industry. The other meaning is associated with the reduction of carbon footprint and minimizing other impacts on the environment.

Many traditional soil cover systems are destined to fail on steep landfill slopes as a result

of excessive erosion, gas pressure buildup, earthquake loads, poor maintenance and/or inadequate post-closure oversight. Closures have shown to lose the integrity of its intended function after site closure and in absence of onsite personnel. The initial construction and reconstruction activity of the cover destroys land to obtain borrow, creates sedimentation issues,

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consumes significant fuel, and produces significant emissions from trucking and operation of heavy equipment.

The goal of an improved closure system should be to first increase the performance and

reliability of its intended function of protecting the environment from groundwater releases and landfill gas emissions. Sacrificing functional integrity for the sake of environmental sustainability is pointless or even harmful from the macro goal of protecting the environment.

A step in the right direction has been some engineers’ reliance on exposed geosynthetics.

Exposed geomembrane cover systems (EGCS) have been successfully used for closures at landfills in the United States for several years. The EGCS represents a positive development in landfill cover system’s design and construction. The use of EGCS minimizes veneer stability issues and eliminates the impacts associated with a soil cover. However, covers using just an exposed geomembrane can have negative aesthetics and require numerous anchor trenches to resist wind uplift. Access can also be very difficult on top of the membrane during post-closure care operations.

This new cover system deals with similar concepts as the EGCS but goes a step further

by combining the impermeable liner with a multiple geosynthetic layers with a synthetic turf yarn. The approach is to utilize the benefits of an EGCS and eliminate the negative aspects of frequent anchoring, poor accessibility and aesthetic issues. This is achieved by providing additional layers of protection, higher friction angles, and homogeneous ballast (as opposed to point loads at anchor trenches) with high drainage capacities. The turf simply serves as aesthetically pleasing, uniform ballast that also provides accessibility, membrane protection and surface water control.

This new approach has all of the positive sustainability characteristics of the EGCS but

also provides an opportunity to obtain “earlier” control of surface emissions. Maximizing control of landfill gas is one of the major goals of the industry and can contribute significantly to the reduction of green house gasses.

The system also provides for a new approach in landfill gas collection (LFG) by using a

geocomposite material at the foundation layer (i.e., below the EGCS) to direct and relieve gas pressure to collection points. This approach has the potential to dramatically improve the landfill gas collection efficiency early in the life of the facility.

Another environmental advantage of this system is providing better options for post-

closure uses. A new trend for post-closure use is solar collection. These fields will employ the use of rigid panels that operate at the highest efficiencies currently available. IMPROVING PERFORMANCE

It is common for engineers to design traditional synthetic and soil covers with a very low factor of safety against veneer failure (factors of safety of 1.1 are many times accepted under dynamic conditions). The post-closure maintenance period also accepts the fact that the system is heavily-reliant on replacing soil loss, re-vegetation, fertilization and storm water repairs. Simply

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improving the performance from this standard traditional design is in itself adding to the environmental sustainability of the cover. The design approach presented here uses synthetic turf and structured geomebranes for final landfill covers. The system requires minimal anchoring and provides a drainage system that can handle intense wind and rain. The components also work together to allow for traffic access during post-closure care and provide for an aesthetically pleasing surface. Comparison of this new approach with prescriptive traditional closures is shown in Figure 1.

Figure 1- Traditional cover compared to new approach.

The cover system of this approach is designed from the bottom up with a lower impermeable layer placed over the soil intermediate cover comprising of: (1) a drain liner geomembrane or textured geomembrane liner and a geonet drainage media, or alternatively a drain liner with studs incorporated in the linear low density polyethylene sheet that serves as the transmissive layer (AGRU US SuperGripNet); (2) the synthetic turf that is engineered with polyethylene fibers with a length of 1.5 to 2.0 inches tufted into two fabrics of woven polypropylene geotextiles, and; (3) a sand layer approximately 0.5 to 0.75 inches that is placed as infill to ballast the material and protect the system against wind uplift. This system has a U.S. patent and is referred to in the industry by the trade name of Closure Turf TM.

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This design approach has a top porous sand ballast layer that resists significant wind uplift forces and disturbs the free stream wind flow. The internal friction angle of the system components provide for a highly stable system without expensive anchor trenching.

Presented in Figure 2 is a diagram that illustrates the multiple forces an exposed cover system must withstand to remain stable. Each force and condition, such as wind loads, seismic, slope angles and rain intensity should be evaluated under severe or worst case conditions as dictated by the design (slope degree and soil sub grade classification) or local climate (wind and rain).

Figure 2 – Design forces acting on cover.

The new system does not present stability issues from sudden failures such as sliding and washout, or from long-term failures caused by soil and wind erosion since there is no vegetated cover. Facility owners and operators of these closures can potentially realize significant cost savings by constructing a cover system with the synthetic grass that does not require the vegetative maintenance, soil grading and replacement that are common with traditional closures.

The amount of sand infill will be based on the wind velocities for the region. The sand

will also provide additional protection of the geotextiles against UV light. The polyethylene yarns durability against UV light, coupled with having infill cover and an upper “sacrificial” geotextile also lends itself well to long-term performance of a closure cover. Field samples taken from covers installed in southern Arizona and central Louisiana have shown that the underlying geotextiles have experienced no identifiable loss of tensile strength ASTM D4595 since the initial installation three years ago. The exposed portions of the yarn (that serve aesthetics only) will maintain the required strength well beyond minimum regulatory post-closure periods. Weatherometer ASTM G147(02) tests performed on the exposed portion of the yarn show less than 10 percent tensile strength loss after 20 years.

Through the combination of these unique geosynthetics components, the landfill operator

can achieve a more reliable and stable cover along with a more environmentally friendly cover system during construction and post-closure maintenance.

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OPTIMIZING SUSTAINABILITY IN CONSTRUCTION

Unlike the traditional soil and geosynthetic composite closures, the system provides a sustainable approach to closing landfills by eliminating soil, removing the need for vegetative maintenance, fertilization and the inherent erosion issues associated with a soil and vegetative cover.

As is the case with exposed geomembrane covers, this composite system also eliminates

the destruction of land for borrow and minimizes the need for on-going maintenance, as is required by a vegetated soil cover (particularly problematic on steep side slopes). Just as is the case on large civil projects and in drainage systems, geosynthetics can provide an opportunity to significantly reduce CO2 emissions. Figure 3 presents a comparison in CO2 emissions for a traditional cover construction and the proposed cover described in this paper.

Figure 3 - Comparison of carbon footprints.

OPTIMIZING SUSTAINABILITY THROUGH CLOSURE PHASING

In addition to saving soil, the proposed new cover can be constructed much faster than traditional covers. The lower construction costs and simplicity of the installation allow the operators to close in smaller increments (3 to 5 acres at a time) once the final grades have been achieved. This results in earlier collection of the landfill gases as opposed to waiting a longer period of time to close large areas (20 to 50 acres) in order to obtain economies-of-scale. Typically, it is impractical for operators to mobilize heavy equipment and procure soil borrow to construct less than 20 acres of closure. The proposed new closure can be installed in an

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economical way in an area as small as 3 acres because of the low mobilization costs and the minimal earthwork required.

According to the EPA there is approximately 10% loss of collection efficiency through

emissions when a gas collection and control system (GCCS) is installed. Without a GCCS in place the amount of landfill gas escaping into the atmosphere can be many times greater. Based on the EPA’s emission loss estimates, and Riley, Park Hayden and Associates experience across the Southeast U.S., it can be reasonably assumed that 2 to 4 cubic feet per minute per acre of surface emissions escape into the atmosphere with a well-operating GCCS with no final cover system in place. Based on these assumptions and typical landfill phasing, the annual and cumulative emission reduction provided by earlier closures using the new cover concept would be significant.

The estimate below is based on 5-acre incremental closures versus a typical 20-acre

incremental closure and assuming a typical landfill filling sequence. An airspace depletion rate of 25 years is used in the total equivalency calculation. Although there are many variables affecting the actual surface emissions, such as the gas generation curve and waste fill depths, a general approximation is provided below to detremine the degree of potential positive impact when implementing more frequent closure phases:

Greenhouse Gas Reduction Estimate

LFG Flow Rate per acre = 2 (assumed) scfm LFG Flow Rate per acre= 1,051,200 scfm/year LFG Methane Content= 50% Net Methane GWP= 21.00 (estimates range from 21 to 23) Direct GHG Emissions Reduction 10 metric tons of CH4 per ac/yr (24.7 metric tons of CH4 per hectare/yr) or, 209,000 kg of CO2 Equivalent (TCO2E) per acre (516,230 Kg of CO2 per hectare)

The total estimated reduction in CO2 emission through smaller, incremental closures can be estimated by assuming a yearly average of 7 acres of additional closure area. An airspace deletion time frame of 25 years is used in the calculation. 209,000 Kg of CO2 per ac/ yr x 7ac x 25 yr = 36,575,000 of CO2 Equivalent

OPTIMIZING SUSTAINABILITY THROUGH END USES

The lack of mowing and vegetation maintenance, such as fertilization and periodic soil replacement will result in a reduction of emissions and improve water quality. However a more significant, positive environmental impact can be realized through the addition of a solar collection facility. There is a current trend to use landfills as solar collectors and the Environmental Protection Agency (EPA) has performed analysis and supports the initiative

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through the office of Solid Waste and Emergency Response. The EPA is encouraging the reuse of closed landfills for siting clean renewable energy facilities.

Placement of renewable energy systems at closed landfills is a relatively new practice. There are a number of challenges that are unique to installing photovoltaic (PV) panels on top of landfills, such as impacting the integrity of the system, stability, maintenance, efficiency losses from dust and shadowing. The closure system presented in this paper helps developers overcome many of these challenges.

There are three types of PV cell materials used in the solar industry. The most efficient

are the polycrystalline and monocrystalline. However, these materials are also the heaviest and require mounting in a rigid frame tied to a foundation (typically concrete footings or pad). There are other type of solar cells that are lighter, normally called thin-film, but they are often less efficient. However it is a pliable material and is much lighter in weight and therefore is better suited to meet the engineering challenges of settlement and integration into an exposed geomembrane. Some of the available PV options are presented in Table 1 below provided by the EPA.

Table 1 – US EPA Table of Photovoltaic Panel Options

Brand Model Watts Weight

(lbs) Watts/Pound Dimensions

(inches) Cell Type*

Uni-Solar PVL-68 68 8.7 7.82 112.1x15.5x0.2 A

Uni-Solar PVL-144 144 17 8.47 216x15.5x0.2 A

Kaneka G-SA060 60 30.2 1.99 39x39x1.6 A

SolarWorld SW175 175 40 4.38 63.9x32x1.6 M

SunWize SW150 150 44 3.41 66.61x30.27 M

REC Solar SCM 210WP 210 48.4 4.33 66.55x39.01x1.69 P

Sanyo 190BA3 190 33 5.75 52x35x1.8 P

HIT Power N 215N/HIP- 215NKHA5

215 35.3 6.10 63.2x32x72.8 P

Mitsubishi MF120EC4 120 25.4 4.72 56.1x25.4x2.2 P

MF185UD5 185 43 4.30 65.3x32.6x1.81 P

Kyocera KC 50T 50 10 5.00 25x26 P

Kyocera KC 130GT 130 26.8 4.85 56.1x25.7x2.2 P

Kyocera KD 180 GX-LP 180 36.4 4.95 52.8x39x1.4 P

*P = polycrystalline; M= monocrystalline; A= amorphous thin film

Integrating the heavier more efficient PV systems with the new proposed closure system is a challenge currently being met by developers who have designed solar fields on top of landfills utilizing the heavier system. Characteristics of the closure system and the surface conditions in which the solar fields are to be developed minimizes many of the issues mentioned above; which may further the goal of the EPA and leaders in the renewable energy industry.

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The most recent closure incorporating the new closure system is located at Crazy Horse Canyon Landfill in Salinas, California. The system, scheduled for installation in the summer of 2011, uses non-penetrating foundations on the top deck of the landfill. Some of the reasons the developer chose to site a solar field on this cover system are:

Protection provided by the turf components allowing for use of the heavier but more

efficient PV system. New frame technology that eliminates fixed anchor points and distributes the stress on the

geomembrane below. Accessibility for maintenance and panel replacement. Differential settlement can be corrected if it occurs to the degree that affects the system. The stability provided by the spikes located on the underside of the geomembrane. Relatively dust free environment promoting efficient solar collection.

Approximately 2,000 panels of monocrystalline cells are designed for a total output of

approximately 1.0 Megawatt. Currently under evaluation is the use of a PV panel racking system on the south side slope that has potential to expand the output by 0.2 Megawatt. The side-slope installations present an additional challenge of designing against sliding failure. The unique membrane incorporated into this system produces a very high interface with the soil foundation layer, thus providing resistance to sliding failure. A trial location has been under evaluation in Tucson, Arizona. The trial consists of rigid panels attached to the impermeable synthetic turf system installed on a 2:1 slope. After two years of evaluation there has been no measurable sliding of the rigid PV units.

The new geosynthetic cover system provides an opportunity for the solar fields to operate

in a clean, very low particulate environment that allows the PV panels to operate at its highest possible efficiency. The nature of the system provides for accessibility, maintenance and replacement of PV panels that have exceeded their service life or be replaced with newer technology panels.

Establishing a renewable energy project such as solar power is a positive trend that can

benefit landfill operators and the community. Solving the unique technical challenges of developing on top of the landfill, and hopefully continued trend of more favorable pricing of PV systems, will result in a practical post closure use that has long evaded the waste industry. CONCLUSION

New geosynthetic applications can improve the reliability and performance of landfill closures. In particular, adding a specialized synthetic turf component to an exposed geomembrane cap can significantly improve membrane protection, accessibility, wind resistance uplift and aesthetics. Additionally, the turf provides for a combination of savings on upfront construction cost and post closure maintenance cost when compared to traditional cover systems.

From a sustainability point of view, the new synthetic closure turf system results in substantial reductions in CO2 emissions from the construction and potential earlier capture of surface emissions.

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The geosynthetic system discussed in this paper provides the ability to integrate the heavier more efficient photovoltaic panels. The advancement of panel frame design and the accessibility provided by the specialized synthetic turf may allow developers to produce solar electricity in a more competitive manner by extending the life of the solar field through panel replacement, and receiving competitive costs through the multiple panel options. ACKNOWLEDGEMENTS Special thanks to Dr. Zehong Yuan or his extraordinary efforts in material evaluation, research and apparatus set up. Also, special thanks to Dr. Demitri Mavris of the Georgia Tech school of Aeronautics for arranging wind tunnel testing. BIBLIOGRAPHY Georgia Tech Research Institute, Aerodynamic Evaluations of ClosureTurf Ground Cover

materials, July 8 2010. Giroud, JP, et al. Uplift of Geomembranes by Wind. Geosynthetics International, Vol. 2, No. 6,

1995. Koerner, Robert M. 2005. Designing with Geosynthetics, 5th Ed. New Jersey: Pearson Prentice

Hall. Kashiwayanagi, M., Sato, M., & Takimoto, J., Six-year Performance of Synthetic-Rubber-Sheet

Facing for the Upper Pond of Seawater Pumped Storage Hydropower Plant. Proceedings of the Eighth International Conference on Geosynthetics, Yokohama, Japan, Vol. 2, pp. 607-610, 2006.

Richardson, Gregory N., PhD, PE, Exposed Geomembrane Covers: Part 1 – Geomembrane

Stresses. GFR Magazine, 2000. SGI Testing Services, Final Report Critical Length and Influence of Seepage Force on Slope

Stability Landfill Cover System. October 20, 2009. The Economist Publication, The Rise of Big Solar, April 17, 2010. TRI Environmental, Soil Loss Testing Report, April 26, 2010. U.S. Army Corps of Engineers, Slope Stability, Engineering and Design Manual. EM 1110-2-

1902, October 31, 2003. U.S. Department of Agriculture, Technical Paper No. 40, SCS, USDA, May 1961. U.S. Environmental Protection Agency, Solar Power Installations on Closed Landfills:

Technical and Regulatory Considerations, September 2009

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THE ROLES OF GEOMEMBRANES IN ALGAE PRODUCTION AT LANDFILLS Y. G. Hsuan and M.S. Olson Drexel University, Department of Civil, Architectural and Environmental Engineering R. Cairncross, Drexel University, Chemical and Biological Engineering S. Spatari, Drexel University, Department of Civil, Architectural and Environmental Engineering S. Kilham, Drexel University, Department of Biology ABSTRACT Waste streams from municipal solid waste landfills may potentially be used as feedstocks to cultivate algae for the production of biodiesel. This paper describes a feasibility study designed to test the potential for using landfill leachate (and eventually landfill gas) as growth media for algae, a critical first step required to convert landfill byproducts to biofuel. The paper also explores three concepts for algae farm production, all using geomembranes as the essential part of the containment systems. They are the following;

geomembrane tubes, floating geomembrane bags, and geomembrane covers in open systems.

INTRODUCTION There are two main waste streams generated from municipal solid waste landfills: landfill gas (LFG) and landfill leachate (LFL). Landfill gas basically consists of 45 to 60% methane (CH4) with an almost equal amount of carbon dioxide (CO2). Other trace gases (less than 5%) include nitrogen, oxygen, ammonia and hydrogen. Methane has been the center of attention in LFG utilization because it is much more potent than CO2 as a green house gas (GHG). On the other hand, CO2 is mostly neglected and released into atmosphere. Regarding leachate, its treatment represents one of the high cost operations of a landfill. Currently there are several leachate management methods: (i) transferring leachate to a wastewater treatment plant, (ii) recycling leachate back to the landfill, and (iii) treating the leachate onsite. Depending on the rainfall intensity of the area, methods (ii) and (iii) still require transporting the excess leachate or treated leachate to waste water treatment plant. In some southern states, wetlands have been proposed and evaluated to treat leachate up to the quantity that can be discharged as storm water. An alternative treatment for leachate is to use microalgae. To our knowledge, there has been only one published feasibility study exploring the use of leachate-tolerant algae for nutrient removal and toxicity reduction of leachate (Lin et al. 2007). Strains of Chlorella microalgae have been shown to remove significant amounts of ammoniacal-N, ortho-P and COD (Aslan and

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Kapdan 2006; Lin et al. 2007) as well as heavy metals and other toxic organic chemicals typically present in leachate (MuÒoz and Guieysse 2006). Preliminary batch experiments indicate the feasibility of using leachate-tolerant algae for nutrient removal and toxicity reduction of leachate (Lin et al. 2007). In support of domestic renewable energy, producing valuable energy products from society’s urban waste holds great promise for the low-carbon, “next” generation liquid bioenergy markets mandated by national policy (EISA, 2007). Many recent research studies have explored the combination of wastewater treatment with microalgal CO2 fixation as a potential pathway for simultaneously removing nutrients and metals from wastewater and CO2 from flue gas (Yun et al. 1997; Mallick 2002; Wang et al. 2008). Similar technology can also be adopted for algae production using the two main landfill’s waste streams to minimize the carbon footprint of a landfill operation, reduce green house gas (GHGs) emissions of the landfill, and reduce landfill waste management costs. Figure 1 shows the hypothetical design concept proposed by a senior student design group at Drexel (DiGiovanni, et al., 2008). The biofuel production section is highlighted in the green box of Figure 1.

Figure 1 - Flow chart illustrating the potential opportunity in generating biodiesel.

LFGCH4 + CO2

Gas Separator

CO2

Leachate Treatment

FacilityOff-site

TreatmentGeneratorElectricity

AlgaePonds Algae Oil

Proteins

Biodiesel

Food

Leachate

Recycle

Landfill

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FEASIBILITY OF ALGAL GROWTH USING LANDFILL LEACHATE

A comprehensive series of batch growth experiments were conducted to evaluate the feasibility of growing algae with diluted leachate and to characterize the resulting changes in leachate composition. Landfill Leachate

Field leachate samples were collected from the Sandtown Landfill of the Delaware Solid Waste Authority (DSWA). Leachate characteristics from Sandtown are shown in Table 1. Note the tremendous differences between minimum and maximum values.

Table 1 - Leachate analysis, courtesy DSWA Sandtown Landfill, Area E between Nov-2003 and Oct-2009

Parameters pH COD (mg/L) BOD (mg/L)

Total Alkalinity

(mg/L) TOC (mg/L) TSS

(mg/L) TDS

(mg/L)

Minimum 5.42 11 2 5 3.2 5 220 Maximum 7.36 8,880 7,470 4,540 2,660 7,520 7,290 Average 6.59 1,599 740 2,141 442 572 3,249

Parameters

Chlorides (mg/L)

TP (mg/L)

Kjeldahl-N Organic-N Ammonia-N Nitrate-N Nitrite-N

(mg/L) (mg/L) (mg/L) (mg/L) (mg/L)

Minimum 5 0.10 1.0 0.5 0.10 0.10 0.02 Maximum 1,740 13.20 1160 465 822 25.00 25.00 Average 674 1.8 320 67.7 267 0.68 1.46

Algae Strain A fresh slant of Chlorella vulgaris (UTEXID 2714) was obtained from the Culture Collection of Algae at the University of Texas (UTEX, Austin, Texas). Algae were grown and maintained in 50-mL glass test tubes containing 25 mL of proteose medium, composed of (per liter) 10 ml NaNO3, 10 ml CaCl2·2H2O, 10 ml MgSO4·7 H2O, 10 ml KH2PO4, 10 ml NaCl, and 1 g proteose peptone (BD 211684), and capped loosely. All cultures were maintained in an environmental chamber (Percival Scientific, model 1-35LLVL) with an average light intensity of 2,500 lux under a 12h light, 12h dark cycle at a temperature between 21-22°C.

Test Design and Results Various ratios of leachate : protease medium were tested as growth media for the algae. Media-filled test tubes were inoculated with algae, incubated in an environmental chamber at 21-22°C, and monitored daily for algal growth. Physical and chemical parameters, which affect the

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growth rate of algae, were studied as well. Select studies are presented and have been divided into two parts: (I) fresh landfill leachate and (II) heated landfill leachate. Algal Growth Measurement The abundance of cells was commonly measured using in vivo fluorometry (Turner Designs) and correlated with concentration using a standard curve of fluorescence versus cell number (Figure 2), as determined by cell counting with a hemacytometer chamber slide. The algal growth rate was determined by shaking the test tube at 60 rpm on a vortex mixer prior to measuring the fluorescence and cell counting. In addition, tubes were visually inspected for color.

Figure 2 - Standard curve of measured fluorescence versus algal cell count.

Part I: Fresh Landfill Leachate

Landfill leachate was diluted with proteose medium at a ratio of 1:75 (leachate:proteose medium). Samples A and B, were inoculated with 5000 and 0 cells/mL of Chlorella vulgaris, respectively. The control consisted of 10,000 cells/mL in proteose medium with no leachate. That said, the choice of a control with a differing cell concentration from the experimental samples was a flaw in this experiment. Duplicate experiments were run for each treatment.

Table 2 - Leachate Dilutions for Part I of this Study

Sample Proteose medium (mL)

Algal cells (cells/mL)

Leachate volume (µL)

Control 25.00 10,000 0 A 24.67 5000 330 B 24.67 0 330

y = 0.0112xR² = 0.9159

02468

10121416182022242628

0 300 600 900 1,200 1,500 1,800 2,100 2,400 2,700

Fluo

resc

ence

(x10

00 R

FU)

Cell number (x1000 cells/mL)

‐176‐ 

Figure 3 shows growth curves for controls 1 & 2 (Chlorella vulgaris with no leachate), depicting approximately 4 days in a lag-phase, 3-4 days in exponential-growth phase and around 7 days to reach a stationary phase. Experiments A1 & A2 did not show good signs of cell growth during the experiment. Algal growth inhibition in experiments A1 and A2 may be explained by Figure 4, which shows the nitrate depletion in non-leachate controls, experiment A, and experiment B (leachate, no algae). In control cultures (grown exclusively on proteose medium), nitrate depletion corresponds with algal growth, with an onset decline coinciding with the end of the algal lag phase (day 4) and complete depletion by day 9, corresponding with the stationery phase of algal growth. In experiments A and B, nitrate concentration rapidly decreased from 250 mg-NO3

-/L to 60 mg-NO3-/L by day 3 (before control algae were out of the lag phase)

and was completely depleted by day six, suggesting bacterial consumption of the nitrate. Sodium nitrate (NaNO3

-) was added on day 7 to raise the nitrate to 100 mg-NO3-/L, as suggested by

Yanqun et al. (2008). However, it became zero again at day eight. NaNO3- was again added on

day 10, and depleted by day 12.

Figure 3 - Growth curves for Chorella vulgaris at different leachate dilutions.

Figure 4 - Nitrate consumption in Chorella vulgaris growth curve studies.

0

50

100

150

200

250

300

1 3 5 7 9 11 13

Nitr

ate

(mg-

N/L

)

Days

control

B

A

Added nitrate

0.0

0.5

1.0

1.5

2.0

2.5

0 2 4 6 8 10 12 14 16

Log

10(F

U)

Days

Control 1Control 2A1A2

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To investigate our speculation that bacteria were outcompeting the algae for nitrate, Part II of this study investigates growth curves of algae grown with heat-killed leachate.

Part II: Heated Landfill Leachate.

Landfill leachate was heated to a temperature of 103°C for 15 minutes using an autoclave on liquid cycle and allowed to cool to room temperature (27-30°C) before mixing. Leachate to proteose medium ratios of 1:50, 1:75 and 1:100 were prepared as shown in Table 3. Algal innocula of 3-day-old cultures were transferred to each test tube to obtain an initial cell concentration of 5,000 cells/mL. There were two duplicates for each treatment.

All algal cultures were incubated in a growth chamber with a light-dark cycle of 12-12 h,

a light intensity of 2,500 lux and a temperature of 21-22°C. Cell abundance was measured daily using fluorometry and cell counts of algae were conducted daily using a hemacytometer in the first four days, and then every four days at Days 8 and 12.

Table 3 - Leachate Dilutions for Part II

Sample Proteose medium (mL)

Algal cells (cells/mL)

Leachate volume (µL)

Control 25 5000 0 A 24.75 5000 250 B 24.67 5000 330 C 24.5 5000 500 D 24.75 0 250

Figure 5 shows growth of Chorella vulgaris at the leachate:proteose medium ratios detailed in Table 3. There were no remarkable differences in algal growth among samples A, B, and C, and all three treatments yielded maximum cell densities comparable to the leachate-free controls. Interestingly, the color of the suspension in the control experiments was observed to change from green to light brown at 18 days, and to be devoid of green after day 20, indicating loss of algal viability. It is possible that additional nutrients in the leachate sustained the algae in stationery phase in the other treatments. The nitrate consumption was not measured during this set of experiments due to a backlog in the necessary reagents. Total nitrogen was measured, and is presented in Figure 6. The total nitrogen reached maximum around 17 days which corresponded to the maximum algal growth.

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Figure 5 - Growth curve of Chorella vulgaris with different dilutions of heat-treated leachate.

Figure 6 - Total nitrogen consumption of Chorella vulgaris in heat-treated experiments.

The next step in the laboratory phase of the project involves characterizing the leachate remediation (reduction in ammonia/ammonium) by the algae and optimizing both algae biomass production and algal lipid content. Biomass productivity and cellular lipid content are two of the major experimental factors influencing the economic feasibility of algal oil for biodiesel production. An ideal process would combine the highest biomass productivity with the highest cellular lipid content. Achieving both outputs simultaneously is difficult, since high lipid cell contents are normally produced under stress conditions such as limited food or nutrients. These stress conditions are subsequently associated with low biomass productivity and, therefore, low overall lipid productivity.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 5 10 15 20 25 30 35

FU (L

og10

)

Days

control 1control 2A1A2B1B2C1C2

050

100150200250300350400

1 6 11 16 21 26 31

Tot

al n

itrog

en, m

g-N

/L

Dayscontrol 1:100 1:75 1:50 1:100, no algae cell

‐179‐ 

ROLE OF GEOSYNTHETICS IN ALGAE FARMING The types of processes for algal growth can be categorized into two general categories; continuous industrial processes and outdoor batch processes. Industrial processes would adopt algae strains that have the greatest growth rate and maximum lipid content. The growth media (particular the nutrient level) and environment (temperature and exposure light) are strictly controlled. The benefit of this process is similar to other manufactured products with high consistency and quality. However, the cost-to-benefit ratio is also very high, challenging the implementation of the technology. In contrast, outdoor batch processes can be cost effective if there is available open space. However, the types of algae strain must be robust to sustain growth under a wide temperature range and light irradiants. Nevertheless, a variety of designs has been proposed depending on the site location and condition, and geomembranes have been incorporated into some of the designs as either the primary containment or as a component of the containment system. A geomembrane tube acting as bioreactor was proposed by Dow Chemical and its partners to grow algae using carbon dioxide saturated salt water (Wald, 2009). The geomembrane is made from a translucent plastic allowing penetration of sunlight. The tubes are laid on the ground at any available outdoor space, Figure 7. The size of the tube is custom made to the needs of the project. Another hypothesized project is to create an algae farm in the water close to the costal line. The farm consists of a series of interconnected geomembrane bags floating on the water so that they do not take up variable land space. The geomembrane bags can be made from translucent or transparent polymers. The advantages of two designs are their mobility, light weight, and flexibility in their dimensions.

Figure 7 – Geomembrane tubes used for algal growth farm (M.L. Wald, 2009).

Alternatively, permanent structures have also been proposed. Raceway ponds are a

popular design that are currently being implemented in several pilot scale projects (Figure 8) (UCSD, 2010). The other option would be a traditional surface impoundment with a geomembrane as the liner material (Figure 9). The challenge for open pond systems is the potential invasion of local algae species which may have lower lipid content than the farming

‐180‐ 

species. The geomembrane that is designed for the tube in Figure 7 can also be used as cover for the open pond system (Ryan et al., 2009).

Figure 8 – Algae farm in a raceway configuration (UCSD).

Figure 9 – Open ponds for algal growth. (source: AgriLife Research Mariculture Lab, Four Bluff, TX.)

CONCLUSIONS AND RECOMMENDATIONS This concept-oriented paper has as its goal the dual uses of landfill gases and landfill leachates for the eventual production of biodiesel fuel. Laboratory studies on fresh landfill leachate and heated landfill leachate were evaluated for their potential as algal growth media. Reduction in the ammonia/ammonium content of landfill leachate is a major consideration in ultimately deriving an algae oil for biodiesel production.

Water Nutrients

CO2

Motorized Paddle

Algae

‐181‐ 

Several concepts of an algae farm using geomembranes are presented including geomembrane tubes, geomembrane bags floating in water, and potentially geomembrane cover used in open system. All are candidate methods presently being evaluated.

REFERENCES

Aslan, S. and I.K. Kapdan, (2006), Batch kinetics of nitrogen and phosphorus removal from synthetic wastewater by algae. Ecological Engineering, 28(1): p. 64-70.

DiGiovanni, K., D. Gryger, M. Henrick, and J. Hildenbrand, (2008), Green Energy from Landfills, Senior Design Project, Department of Civil, Architectural, and Environmental Engineering, Drexel University.

UCSD (2010), http://algae.ucsd.edu/research/algae-farm.html, December 21, 2010

EISA (2007) Energy Independence and Security Act of 2007, Pub.L. 110-140, U.S. Congress, 2007.

Lin, L., G.Y.S. Chan, B.L. Jiang, and C.Y. Lan, (2007), Use of ammoniacal nitrogen tolerant microalgae in landfill leachate treatment. Waste Management, 27(10): p. 1376-1382.

Mallick, N., (2002) Biotechnological potential of immobilized algae for wastewater N, P and metal removal: a review. BioMetals, 15: p. 377-390.

MuÒoz, R. and B. Guieysse (2006), Algal-bacterial processes for the treatment of hazardous contaminants: A review. Water Research, 40(15): p. 2799-2815.

Ryan, C., et al., (2009), Cultivating Clear Energy – The Promise of Algae Biofuels, National

Research Defense Council, page 92. Wald, M.L. (2009), The New York Times, June 29, 2009. Wang, M.Q., GREET 1.7. 2007, Center for Transportation Research: Argonne National

Laboratory. p. Transportation Fuel-Cycle Model.

Yun, Y., et al., (1997), Carbon dioxide fixation by algal cultivation using wastewater nutrients. J Chem Technol Biotechnol, 69.

‐182‐  

TRADITIONAL VERSUS EXPOSED GEOMEMBRANE LANDFILL COVERS: COST AND SUSTAINABILITY PERSPECTIVES

Robert M. Koerner, Ph.D., P.E., NAE Geosynthetic Institute, Folsom, PA USA ABSTRACT

All municipal solid waste (MSW) landfills require a final cover system to be placed over the waste mass within a relatively short period of time. In the USA this is within about one-year. Furthermore, this final cover must be maintained by the landfill owner or operator for thirty-years; called the “post-closure care period”. An alternative to this traditional final cover is to use an exposed geomembrane cover for the 30-year post-closure care period and then construct the final cover. There are many advantages to this alternative strategy which are elaborated upon in this paper. Most importantly, the paper presents both a cost comparison and a sustainability comparison between the two alternatives. It is shown that the exposed geomembrane cost alternative is 30% of a traditional cover and the carbon footprint (based upon the amount of CO2 generated) for the exposed geomembrane alternative is only 18% of the traditional cover.

A closing section is also included as to landfill strategies going beyond 30-years. A

recent GSI survey shows that state regulatory agencies are quite uncertain in this regard. Two alternatives appear to be as follows:

(a) If the traditional final cover is compromised because of the waste’s large total and

differential settlement it must be removed, additional waste can be added, and then must be reconstructed.

(b) When the exposed geomembrane cover has degraded it must be removed, additional waste can be added, and then a traditional final cover installed.

These are, of course, site-specific situations and other possibilities exist as well. It appears as though a dialogue among the parties involved as to various possible strategies beyond the thirty-year post-closure care period would be a worthwhile endeavor. INTRODUCTION This paper addresses municipal solid waste (MSW) landfill closures after the waste mass has been placed to its regulated height and footprint. Regulations are reviewed which indicate that a traditional multi-layer final cover is to be placed within 30 to 720 days and then must be maintained for a 30-year post-closure care period. During this time frame, the traditional multi-layer final cover must function as intended. Considering the large amount of settlement, proper functioning of the barrier layer (particularly compacted clay liners) is easily compromised. Veneer slope stability as well as surface erosion are also ongoing concerns. Maintenance can be (and often is) time consuming and costly.

‐183‐  

The paper suggests using an alternative of an exposed geomembrane cover during this initial 30-year time frame. Durability can be assured and maintenance is straightforward and readily achieved. Cost and sustainability comparisons between the traditional and geosynthetic alternatives are presented. TRADITIONAL FINAL LANDFILL COVERS Final covers at MSW landfills in America* must follow RCRA Regulations, Title 40, Part 258.60 whereby the following criteria must be met:

The permeability of the barrier must be less than 1 10-5 cm/sec, or less than the liner’s permeability.

The system must minimize infiltration into the waste mass. The system must minimize erosion. The system must be placed within one-year of the final waste placement. Alternatives can be approved by the State’s Director of Environmental Protection.

RCRA Regulations Part 258.61 also have the following criteria in regard to “post-closure care”:

The time frame is for 30-years. The cover must maintain its integrity and effectiveness. Leachate collection must be ongoing. Groundwater must be monitored. Landfill gas must be monitored and/or collected.

Lastly, RCRA Regulations Part 258.72 addresses financial assurance during this post-closure care period as follows:

Financial assurance costs must be estimated by a third-party firm. It must be based on the most expensive maintenance costs during the 30-year time frame. There must be an annual adjustment for inflation. Continuous coverage must be provided until the owner is released by demonstration of

compliance with the post-closure plan by an independent registered professional engineer or approved by the State Director.

Within the context of the above criteria, the vast majority of MSW landfill covers (the exception being in arid areas) have six layered components as shown in Figure 1. Koerner and Daniel (1997) describe each layer, their purpose, and counterpart the use of natural soils vis-à-vis geosynthetics. This particular cross section, with the barrier layer being a geomembrane over a compacted clay liner (i.e., a GM/CCL composite), is considered the “traditional” cover in this paper.

                                                            *It should be noted that many environmental agencies worldwide have similar prescriptive regulations for MSW landfill final covers; see Koerner and Koerner (2007). 

‐184‐  

Fig. 1 – Six typical layers to be considered in final cover design (Koerner and Daniel, 1997).

CONCERNS OVER TRADITIONAL FINAL COVERS There are many concerns over the use of a final cover as indicated in Figure 1 particularly when it is installed within one year after final waste placement due to its subsequent behavior. Perhaps the major consideration is the large amount of settlement of MSW over time. See Figure 2 where settlement values, as a percentage of original waste thickness, can be 30%, and greater. Even further, note that the settlement in several of the case histories is still ongoing.

Fig. 2 – Total settlement data from number of municipal solid waste landfills; after Edgers, et al. (1990); König, et al. (1996); Spikula (1996).

‐185‐  

In undergoing such settlement, the natural soils (particularly compacted clay liners will very likely crack and lose their initially placed low permeability; see Heerten and Koerner, 2009 among others. The emergence of bioreactor landfilling (Reinhart and Townsend, 1998) only exacerbates such settlement with respect to both time and amount. Accompanying such large landfill settlements is the possibility of differential settlement whereby localized depressions are formed. These will act as “bathtubs” and surface water will be captured and eventually diffuse through the barrier layer even if it is not breached. Figure 3 shows several cases of such localized landfill settlement depressions. Other adverse aspects of traditional landfill covers, which can readily occur within the 30-year post-closure care period, are the following:

Erosion of topsoil and some or all of the soil protection layer. Gas bubbles (called “whales”) pushing the geomembrane barrier up through the

overlying layers. Veneer sliding of the cover soil above the lowest shear strength interface within the

multilayered cross section. Burrowing animals within the topsoil and protection soil thereby compromising

performance of the system. Trees and other major vegetation growing in the soil above the drainage layer with roots

that penetrate it causing excessive clogging. The net result of the current RCRA Regulations as far as placement of traditional MSW landfill covers is concerned is a situation with numerous pitfalls and obstacles challenging its long-term efficiency within this initial 30-year time period. This, of course, says nothing about the costs involved which will be discussed later.

‐186‐  

Differential settlement in a landfill cover in Pennsylvania

Differential settlement of a landfill cover in Florida

Differential settlement of a landfill cover in Ohio

Fig. 3 – Various cases of differential settlement in final covers at MSW landfills.

‐187‐  

EXPOSED GEOMEMBRANE LANDFILL COVERS In the 25-years since the RCRA Regulations were promulgated by the U. S. Environmental Protection Agency all geosynthetics, including geomembranes, have made great strides in their formulations and manufacturing. Issues such as degradation by chalking or powdering, as well as stress cracking, have been eliminated (or greatly mitigated) when selecting the proper resin and additive package; the latter consisting of processing stabilizers, long-term antioxidants, and carbon black or colorants. This is not to say that geomembrane field problems have not occurred, but when properly selected and formulated an exposed lifetime of thirty years (even in hot climates) is achievable. To substantiate this statement, ongoing results of a seven-year laboratory study being conducted by GSI follow. Figure 4 is a mosaic of four different resin types* that are being using in many exposed geomembrane applications, e.g., dams, reservoirs, canals, etc. Figure 4a is the percentage strength retained from the original material, and Figure 4b is the complimentary percent elongation retained. The exposure procedure for all materials is according to ASTM D7238 at 70°C. The subsequent tensile testing to obtain the numeric data is per D6693 for HDPE, LLDPE and fPP, and D882 for EPDM. The results are tabulated in Table 1.

020406080

100120

0 10000 20000 30000 40000 50000 60000

Perc

ent S

tren

gth

Ret

aine

d

Light Hours

HDPE per GM13 at 70°C

LLDPE per GM 17 at 70°C

fPP per GM 18 at 70°C

EPDM per GM 21 at 70°C

0

20

40

60

80

100

120

0 10000 20000 30000 40000 50000 60000

Perc

ent E

long

atio

n R

etai

ned

Light Hours

HDPE per GM13 at 70°C

LLDPE per GM 17 at 70°C

fPP per GM 18 at 70°C

EPDM per GM 21 at 70°C

Fig. 4 – Comparison of strength and elongation retained of four geomembranes undergoing UV laboratory exposure per ASTM D7238 at 70°C.

                                                            *HDPE = high density polyethylene   LLDPE = linear low density polyethylene   fPP = flexible polypropylene   EPDM = ethylene propylene diene terpolymer 

‐188‐  

Table 1 – Laboratory Weatherometer Results for Various Geomembranes

Type Specification1 Strength Ret. (%) and Exposure

(lt. hrs.)

Elongation Ret. (%) and Exposure

(lt. hrs.)

Comment Lifetime2

HDPE LLDPE fPP EPDM

GRI-GM13 GRI-GM17 GRI-GM18 GRI-GM21

78% @ 51,000 50% @ 48,000 65% @ 40,300 82% @ 43,200

74% @ 51,000 50% @ 43,500 61% @ 40,300 52% @ 43,200

ongoing halflife reached ongoing ongoing

42+ yrs. 36 yrs. 33+ yrs. 36+ yrs.

Notes: 1. See the GSI Website at <www.geosynthetic-institute.org> for the most recent version 2. Based on a correlation factor of 1200 lt. hrs. = 1.0 yr. in a hot climate like west Texas and

Southern California. It will be noticed in Table 1 that a 50% reduction from the as-received material properties is considered the half-life and this value is used in the lifetime prediction. Only the LLDPE has reached this value presently although the EPDM is close. The correlation factor was based on four field failures (two in West Texas and two in Southern California) of flexible polypropylene geomembranes which had archived samples. These samples were also tested per D7238 at 70°C until halflife and the number of light hours obtained accordingly; see Figure 5a. This value compared to the actual field performance time resulted in a correlation factor of 1200 light hours being equivalent to 1.0 year of service life in a hot climate; see Figure 5b. In essence the laboratory incubation is providing an acceleration factor of 6.1 over field service time in these hot climates. The point to be taken from the laboratory information just presented is that several geomembrane types can readily satisfy the 30-year time required for post-closure of landfills. In a less severe climate than Figure 5 indicates, the geomembranes being evaluated can far surpass 30-years. To the authors this data suggests that an exposed geomembrane is a viable option to a traditional one as indicated by the layered system shown in Figure 1. Figure 6 shows a number of exposed geomembrane covers which have been performing well over time. Perhaps the biggest issue over exposed geomembranes is their anchorage against wind uplift. This issue has been largely solved using parallel downslope anchor trenches as described by Hullings (2009).

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(a) Actual test data (a) Laboratory incubation responses of archived field samples of fPP geomembranes which had

prematurely failed in the field

Method Field Lifetime (yrs.)

Field Location

Lab Time to 50% (lt. hr.)

Correlation Factor (lt. hrs./1.0 yr.)

fPP-1 fPP-R1 fPP-R2 fPP-R3

~ 2 ~ 8 ~ 8 ~ 2

W. Texas W. Texas So. Calif. So. Calif.

1800 8200 11200 2500

900 1025 1400 1250 1140*

*Use 1200 lt. hr. = 1.0 year in a hot climate

(b) Data interpretation to obtain a correlation factor

Fig. 5 – Establishment of a correlation factor between field failure times and halflife in a laboratory weatherometer per ASTM D7238 at 70°C.

-20

0

20

40

60

80

100

120

0 5000 10000 15000 20000

Perc

ent

Stre

ngth

Ret

aine

d

Light Hours

fPP-1 (1.00 mm)

fPP-R (1.14 mm)

fPP-R2 (0.91 mm)

fPP-R3 (0.91 mm)

‐190‐  

Fig. 6 – Several exposed geomembrane covers on MSW landfills; compl. of authors, Gleason, et

al. (1993) and Hullings (2009).

‐191‐  

COST COMPARISON OF TRADITIONAL AND EXPOSED GEOMEBRANE COVERS When comparing a traditional landfill cover as indicated in Figure 1, to an exposed geomembrane cover as shown in Figure 6, the elimination of surface layer, protection layer, and drainage layer will obviously economically favor the exposed geomembrane solution. That said, the exposed geomembrane solution will still require a gas collection layer and an underlying foundation layer. It will also require a thicker (hence, more robust) geomembrane and these considerations will be reflected in the cost analysis to follow. A 1.0 mm LLDPE was used for the traditional cover and a 1.5 mm fPP/EPDM for the exposed. In the following cost analysis a landfill cover in the Philadelphia, Pennsylvania region is envisioned. The estimated installed unit prices are current as of Summer 2010; see Table 2. These unit prices are then extended to a hectare as shown in Figure 7. As anticipated, the exposed geomembrane cover is only a fraction (30%) of the cost of a traditional final cover over the 30-year period envisioned. Of course, this leaves open the question of performance after 30-years. If the traditional final cover and exposed geomembrane covers are both depreciated at this time, the cost comparison is valid. If, however, the traditional final cover is still functional, or is partially functioning and can be reasonably remediated, the cost comparison is invalid. In a converse sense, the very large settlement of the waste mass at the end of this 30-year period (recall Figure 2) is recoverable for additional waste placement. This cannot be accomplished if a traditional final cover of the type shown in Figure 1 is deployed. In contrasting both of these issues it is fully realized that site-specific conditions will prevail. CARBON FOOTPRINT OF TRADITIONAL AND EXPOSED GEOMEMBRANE COVERS A flow-chart containing each layer will be used to compare the carbon footprints of a traditional final cover and an exposed geomembrane cover. Data on CO2-values were obtained from U.S. EPA (2005), University of Bath (2008) and the German Institute for Energy Conservation (1999); see Table 3 where the units are Kg CO2/Kg of specific materials as well as Kg CO2/gallon of diesel fuel for the transportation costs. The flow chart of Figure 8 presents the calculated values of kilograms of CO2 liberated for the respective materials per square meter and then extended per hectare. Diesel fuel is based on truckloads of the various materials from their estimated sources to a hypothetical site in the Philadelphia, Pennsylvania area. These two values (materials and transportation) are then added and transposed onto Figure 8 for each layer of material of the two respective alternatives and totaled. Here it is seen that the CO2 footprint of the exposed geomembrane cover is only 20% of the traditional multi-layered cover shown in Figure 1.

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Table 2 – Estimated Installed Costs for Various Layers of Landfill Covers

Layer (Top-to-Bottom)

Traditional Landfill Cover ($/m2)

Exposed Geomembrane Cover ($/m2)

Seeding and vegetation 0.90 - Topsoil; 150 mm 36.00 - Protection Soil; 750 mm 22.80 - Drainage composite; 6.3 mm 7.30 - Geomembranes; 1.0 and 1.5 mm 6.50 9.20 GCL-reinforced 4.20 4.20 Geotextile; 520 g/m2 3.80 3.80 Soil foundation layer 9.20 9.20 Waste proof rolling 0.90 0.90 TOTALS 91.60 27.30

Table 3 – Embodied Energy and Carbon Values for Layers of Landfill Cover Components; ref. U.S. EPA (2005), University of Bath (2008), and the German FFE (1999)

Layer

Top-to-Bottom Carbon Values

(Kg CO2/Kg material) seeding and vegetation 0.190 Kg CO2/Kg topsoil 0.090 Kg CO2/Kg protection soil 0.023 Kg CO2/Kg drainage composite (PE) 1.7 Kg CO2/Kg geomembrane (PE) 1.7 to 2.0 Kg CO2/Kg geosynthetic clay liner 0.22 Kg CO2/Kg geotextile (PP) 2.7 Kg CO2/Kg soil foundation 0.023 Kg CO2/Kg proof rolling 0.045 Kg CO2/Kg diesel fuel 10.1 Kg CO2/gallon

‐193‐  

Traditional or Geosynthetic Approach?

Soil foundation layer

Proof rolling of waste

Geotextile

GCL

Geomembrane

Drainage composite

Protection soil

Topsoil

Seeding and vegetation

Option 1 Traditional

Total Cost

$360,000/ha

$228,000/ha

$73,000/ha

$65,000/ha

$42,000/ha

$38,000/ha

$92,000/ha

$9000/ha

$916,000/ha

Soil foundation layer

Proof rolling of waste

Geotextile

GCL

Geomembrane

Option 2 Geosynthetics

Total Cost

$92,000/ha

$42,000/ha

$38,000/ha

$92,000/ha

$9000/ha

$273,000/ha

Fig. 7 – Flowchart comparing costs in units of “$/ha”.

$900/ha

‐194‐  

Traditional or Geosynthetic Approach?

Soil foundation layer

Proof rolling of waste

Geotextile

GCL

Geomembrane

Drainage composite

Protection soil

Topsoil

Seeding and vegetation

Option 1 Traditional

Total CO2 Footprint

227,000 Kg CO2/ha

288,000 Kg CO2/ha

19,000 Kg CO2/ha

19,000 Kg CO2/ha

13,000 Kg CO2/ha

16,000 Kg CO2/ha

70,000 Kg CO2/ha

200 Kg CO2/ha

652,400 Kg CO2/ha

Soil foundation layer

Proof rolling of waste

Geotextile

GCL

Geomembrane

Option 2 Geosynthetics

Total CO2 Footprint

32,000 Kg CO2/ha

13,000 Kg CO2/ha

16,000 Kg CO2/ha

70,000 Kg CO2/ha

200 Kg CO2/ha

131,200 Kg Co2/ha

Fig. 8 – Flowchart comparing carbon footprints in units of “Kg CO2/ha”.

200 Kg CO2/ha

‐195‐  

IS AN EXPOSED GEOMEMBRANE ALLOWED BY REGULATORS AND WHAT HAPPENS AFTER 30-YEARS? In order to use an exposed geomembrane cover for the 30-yer post-closure care period, approval by the appropriate state environmental agency must be obtained. A GSI survey of 2009 queried the fifty American states with a response from 32 of them. Figure 9 shows information gained insofar as the maximum time allowed before final cover is placed. It ranges from 30 to 360 days, with one state allowing 720 days.

Fig. 9 – Maximum time allowed after final waste is placed and before final cover is placed by various states.

More significant in the context of an exposed geomembrane cover, is whether or not it is even allowed. In this regard, the various state regulators gave the following responses.

Yes – 7 No – 16 Conditionally – 9 Undecided – 18

Other responses to various questions in the survey were as follows: Regarding the necessity of an actual performance bond, fifteen states required an insurance bond while seventeen required that the owner must instead demonstrate financial assurance. The time duration for such bonds is the standard thirty years for twenty-two states. Two states required forty years, and eight require a bond for the post-closure period of undesignated duration. The amount of bond varies from state-to-state, but one state is quite specific at $100,000 per acre adjusted for inflation. Regarding the situation of times beyond the initial thirty-year post closure period, sixteen states are beginning to address the issue and several have a draft policy or are considering time extensions. Comments like “possibly indefinite”, until the waste is “stabilized” or “as long as necessary” are also mentioned.

060

120180240300360420480540600660720

AL AZ AR CA DE ID IA IL IN KS KY MEMA MI

MSMO NE NJ

NM NY OK PA RISD TN TX UT

VA WV WA WIWY

Various States

Tim

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ays)

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SUMMARY AND CONCLUSIONS The contrast of cost and carbon footprint of a multi-layered final cover versus an exposed geomembrane cover for closed MSW landfills is quite dramatic. Shown in this paper the values are as follows:

The cost of an exposed geomembrane cover is 30% of the traditional cover. The CO2 footprint of an exposed geomembrane cover is 20% of the traditional cover.

These contrasts speak well for the initial 30-year post-closure care period, but they beg the question as to an appropriate strategy for even longer time frames. This issue is clearly on the minds of the regulatory community and undoubtedly the landfill ownership community as well. Perhaps, in this regard, it is time to begin to seriously explore the possible alternatives that lie ahead. ACKNOWLEDGEMENTS This paper is made available through financial assistance of the Members, Affiliated Members and Associate Members of the Geosynthetic Institute (GSI). We sincerely thank them in this regard. See our website at www.geosynthetic-institute.org for their identification and contact persons. REFERENCES ASTM D882 – Test Method for Tensile Properties of Thin Plastic Sheeting. ASTM D6693 – Test Method for Determining Tensile Properties of Nonreinforced Polyethylene and Nonreinforced Flexible Polypropylene Geomembranes. ASTM D7238 – Test Method for Effect of Exposure of Unreinforced Polyolefin Geomembranes to Fluorescent UV Condensation Apparatus. Edgers, L., Noble, J. J. and Williams, E. (1990), “A Biologic Model for Long Term Settlement in Landflls, Tufts University, Medford, MA. FFE Forschungsstelle für Energiewirtschaft der Gesellschaft für praktische Energiekunde e.V. (1999): Ganzheitliche Bilanzierung von Grundstoffen und Halbzeugen. Teil I Allgemeiner Teil. eil II Baustoffe. Teil III Metalle. Teil IV Kunststoffe. München. Gleason, M. H., Houlihan, M. F. and Giroud, J.-P. (1998), “An Exposed Geomembrane Cover System for a Landfill,” Proceedings 6th ICG Conference, Atlanta, George, IFAI Publication, pp. 211-213. Heerten, G. and Koerner, R. M. (2008), “Cover Systems for Landfills and Brownfields,” Journal of Land Contamination and Reclamation, Vol. 16. No. 4, London, pp. 343-356.

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Hullings, D. E. (2009), “Exposed Geomembrane Cover Details,” Proceedings GRI-22 Conference, Salt Lake City, GSI Publication, Folsom, PA, pp. 77-85. Koerner, R. M. and Daniel, D. E. (1997), Final Covers for Solid Waste Landfills and Abandoned Dumps, ASCE Press, Reston, Virginia, 256 pgs. Koerner, R. M. and Koerner, J. R. (2007), “GRI’s Second Worldwide Survey of Solid Waste Landfill Liner and Cover Systems,” GRI Report No. 34, GSI Publication, Folsom, PA, 137 pgs. König, D., Kockel, R. and Jessberger, H. L. (1996), “Zur Beurteilung der Standsicherhert und zur Prognose der Setzungen von Mischabfalldeponien,” Proc. 12th Nürnberg Deponieseminar, Vol. 75, Eigenverlag LGA, Nürnberg, Germany, pp. 95-117. Reinhart, D. R. and Townsend, T. G. (1998), Landfill Bioreactor Design and Operation, Lewis Publishers, Boca Raton, Florida, 189 pgs. Spikula, D. (1996), “Subsidence Performance of Landfills: A 7-Year Review,” Proc. GRI-10 Conference on Field Performance of Geosynthetics and Geosynthetic Related Systems, GSI Publication, Folsom, PA, pp. 237-244. U. S. EPA (2005), “Emission Facts,” Office of Transportation and Air Quality, EPA 420-F-05-001, February. University of Bath (2008), “Inventory of Carbon and Energy,” Version 1.6a, see www.carbonneutralfuel.co.uk.